History - Part 1 - 1918 to 1944

The Kaiserreich arises once more

After World War I, Prussia (East and West), Posen, Silesia (though half still went to Germany), Mecklenburg, Pomerania and Schleswig-Holstein, as well as parts of Hannover, Saxony and northern Brandenburg, seceded from the rest of Germany and formed the "Kaiserreich Preußen" ("Empire of Prussia", mostly known in English as the "Prussian Empire"; demonym "Prussian"), in late 1918 / early 1919, under the rule of Kaiser Friedrich IV (* 6 May 1882 in Potsdam; † 4 December 1956 in Königsberg), who was born as Crown Prince Friedrich Wilhelm von Preußen. The plan for the secession was codenamed "Oststaat-Plan II" ("Eastern State Plan II"). The Empire's capital was the city of Königsberg in East Prussia.
The formation of the so-called "Oststaat" happened shortly after "Unternehmen Schwanengesang" (German for "swan song"), which was personally planned and led by German Crown Prince Wilhelm and King Gustaf V of Sweden. They had predicted the German Revolution of 1918/19 and the peace negotiations with the Entente and wanted to prevent the Imperial German Fleet falling into British hands. During the operation large parts of the Imperial German Navy were seized by Loyalist German forces and Swedish soldiers and the Kiel Mutiny was violently crushed. As planned, all seized ships were then sailed to neutral Sweden, where they became part of the Freie Deutsche Reichsmarine, which would soon become the Imperial Prussian Navy.
Through the good connections the Kaiser had with Sweden and established with the USA, he managed to protect Prussia until he could rebuild the German military (as the Reichsstreitkräfte, in English "Imperial Armed Forces"). The Treaty of Versailles did not apply to Prussia (the Entente was satisfied with what they perceived as a "severely weakened, divided Germany"), so all branches of its military were expanded and modernized extensively. Prussia also refused to accept the Washington Naval Treaty and any other treaty or agreement limiting military spending or military construction. This, together with new Prussian capital ships built (in addition to the capital ships seized in Schwanengesang), was the main reason for the universal renouncement of the Washington Naval Treaty (and the subsequent adoption of the Prussian-championed "Hamburg Naval Treaty").

Flag of Prussia from 1918 to 1947. The flag of the Prussian Empire was the same as the flag of the Kingdom of Prussia.

From the beginning, Prussia's economy "boomed", thanks in no small part to the Kaiser's "economic brillance" (though the wealth of his wife's family surely helped as well). Throughout its existence Prussia was mostly unaffected by all economic and financial crisises of the time.

Due to the discrimination they suffered in the newly formed Poland, many Germanic people fled from it in the time from 1918 to 1924 and were successfully integrated into Prussia.
In addition, many Russians that opposed communism fled from Russia to Prussia, where they were allowed to stay for a limited amount of time. However, if they could prove that they had at least some German ancestry or "served Prussia or its interests exceptionally well", they were allowed to become citizens of Prussia, but had to undergo rigorous Germanisation. It is estimated that about 200,000 Deutschrussen ("German-Russians") became Prussian in this way.
Additionally, many people of the German diaspora were enticed to emigrate to Prussia under the higly successful "Kommt zurück!" ("Come back!") program from 1920 to 1944. These included millions of German Americans from both South and North America, Germans from Hungary, Romania and the Baltic, including the Siebenbürger Sachsen ("Transylvanian Saxons", circa 600,000), Bessarabiendeutsche ("Bessarabia Germans", circa 150,000) and the Donauschwaben ("Danube Swabians", circa 1,500,000). All were integrated seamlessly into the Empire, undergoing rigorous Germanisation, and were a significant factor in Prussia's "rise to power".
Also, a substantial number of Austrian monarchists migrated to Prussia, as they felt that Kaiser Friedrich was "the last hope for the Germanic monarchy". These monarchists were highly loyal to the Kaiser and affectionately referred to him as "Kaiser Fritz" or "Kaiser Franz". Adding to growing Prussian population also were great numbers of Deutschamerikaner ("German Americans"), who were enticed by generous benefits afforded to immigrants with German ancestry (a famous example: General Robert Carter, formerly a citizen of Virginia) and often also fled from the anti-German sentiment which had grown in the USA during World War I. Substantial numbers of Deutschamerikaner came from California, Texas, Pennsylvania, Ohio, Iowa, Minnesota, Wisconsin, Nebraska, and the Dakotas, but also from Florida and Virginia. Smaller numbers came from other US states such as Arkansas. All Deutschamerikaner were Germanised.
Numerous other immigrants to Prussia (all of German ancestry) came from several other countries, including Australia, Chile, Argentinia, Peru, Yugoslavia, Switzerland, Italy, France, and Britain.
In addition to the seamlessly integrated and Germanised immigrants highly effective "population growth programs" with the names of "Aphrodite" and "Venus" were instituted in 1919.

Prussia also became a haven for monarchists and nobles from all over Germany, including most former ruling German dynasties (e.g. the House of Wittelsbach, the House of Württemberg). They became an important part of Prussian politics - forming the so-called "Princely Faction" - and the Prussian military and also greatly influenced Prussian society.

Portrait of Kaiser Friedrich as the crown prince of Germany; circa August 1905

The Prussian-Polish War

On 5 January 1929 Princess Agnes of Hohenzollern, third child of Kaiser Friedrich, was murdered by the Polish anarchist Pavel Rasky, which sparked war. The Prussian armed forces, supported by Sweden, invaded Poland, which was supported by Lithuania. This became known as the "Prussian-Polish War" (as the fighting against Lithuania did not merit too much attention) and lasted only one month (6 January 1929 - 6 February 1929).

Prussian officers (still wearing old model uniforms) in Königsberg; circa 1929

Prussia gained several territories after Poland's and Lithuania's unconditional surrender.
In the following years the newly gained areas were successfully integrated into the Empire, both economically and militarily. The Polish population of these areas was completely expelled in 1929/30, with most of these Poles fleeing to the unoccupied parts of Poland.

From 1930 to 1947, even more people of German descent from Austria, Switzerland, Czechoslovakia (Sudetenland), Yugoslavia, Russia, and Hungary flocked to Prussia, due to the "opportunities" and incentives it offered to "Germanic settlers in the East".

Foreign policy / Foreign relations / Involvement in civil wars and revolutions

Best friend of the new Germany

True to its roots, Prussia had always sought a tight partnership with Germany; however, Kaiser Friedrich despised the Republic of Weimar, calling it the "Saurepublik" ("Swine-Republic"). This was one of the reasons why he vehemently supported the NSDAP.
In 1928 the NSPAP (Nationalsozialistische Preußische Arbeiterpartei, "National Socialist Prussian Worker's Party") was founded by supporters of the German national socialists as a branch of the NSDAP.
The Prussian Reichstag elections of 1934 were won in a landslide by the "Deutsche Monarchenpartei" ("German Monarch Party", DMP for short; a monarchist party founded and led by nobles from all over Germany who had sought refuge in Prussia after 1918/19; the most important Prussian political party). The NSPAP subsequently formed a reluctant coalition with the DMP (on direct order of Kaiser Friedrich), which proved to be an important step to reconcile (and eventually mostly merge) Prussian Monarchism and National Socialism, the two most important political positions in Prussia and Germany. The NSPAP was merged with the NSDAP when Prussia reunited with Germany in 1947; the NSDAP and the DMP are the two strongest polticial porties in modern-day Germany, representing similar positions.
In 1930 the Prussian SA and SS were founded, followed by the Kaiserliche Bewaffnete Schutzstaffel (KBSS, essentially the Prussian Waffen-SS) in 1941.
After the 1930 national-socialist "Machtergreifung" in Germany, Prussia sought to establish close diplomatic and economic relations with the "Neues Deutschland" ("New Germany", a term used in Prussia to refer to Germany under national socialist rule). This came to pass with the "Vertrag von Bonn" ("Treaty of Bonn") of 1 March 1930. This treaty marked the beginning of a close Prussian-German economic and military alliance.

Early Prussian SS men; circa 1930/31

Prussian General Dietrich Greif on a visit to Germany, talking with some local women at Castle Passau; circa January 1935

Adolf Hitler reviews a Prussian guard unit after a visit to the Prussian "Deutsches Opernhaus"; circa 1936

Austrian Civil War

On 12 February 1934 the Austrian Civil War (also called the February Putsch) started with skirmishes between socialist and conservative-fascist forces. The clashes started in Linz and took place principally in the cities of Vienna, Graz, Bruck an der Mur, Judenburg and Steyr, but also in some other industrial cities of eastern and central Austria. The fighting continued until 16 February 1934.
The Prussian army, having had established military bases near Linz, Steyr and Vienna in 1930 under the "Preußisch-Österreichischer Militärkooperationsvertrag" ("Prussian-Austrian Military Cooperation Treaty"), intervened in the fighting, crushed the insurgents and occupied the cities of Vienna, Steyr, Linz and Graz. The bases were used by the 1st battalion of the 5th Infantry Regiment (of the 2nd Infantry Division 'Hindenburg'), the 2nd battalion of the 3rd Panzer Regiment (of the 2nd Panzer Division 'Mackensen') and the 3rd battalion of the 1st Gebirgsjäger Regiment (of the 1st Gebirgsjäger Division 'Erzherzog Eugen').
On 16 February a company of Prussian Gebirgsjäger from the Vienna military base, supported by six A8 "Fuchs" tanks from the base near Steyr, stormed the Federal Chancellery of Austria and took the Austrian government officials there, including Chancellor Engelbert Dollfuß, hostage. Similar scenes took place in numerous other Austrian cities, including Linz, Graz and Steyr, where Prussian soldiers unseated the local government. They were supported by troops from the Austrian Bundesheer, whose leadership had secretly helped to plan and execute the February Putsch (as the events from 12 to 18 February 1934 are now known).
Following this, the entire Austrian government was forced to resign and a government under the DNSAP (the Austrian National Socialist Party) was installed. Former Chancellor Engelbert Dollfuß, as well as 21 other officials, were secretly executed by an Austrian firing squad in Vienna on 18 Feburary.
Following the "takeover" of the DNSAP, Austria was officially annexed by Germany on 21 February (this was called the "Anschluß"). Prussia supported the annexation.

Prussian soldiers in Vienna; circa 15 February 1934

Adolf Hitler holding the famous "Anschluß-Speech" on Vienna's Heldenplatz; 22 February 1934

Indian Revolution

Prussia secretly supported the (violent) Indian Revolution of 1928 to 1933, which resulted in India's independence from Britain in 1933, and the formation of an independent Indian government under the leadership of Mahatma Gandhi and Subhas Chandra Bose (who is mostly referred to by the honorific "Netaji" meaning "Respected Leader" in Hindustani).
Prussia and India entered a close military alliance with the "Vertrag von Kalkutta" ("Treaty of Calcutta") in January 1934. The newly formed Indian military was trained and organised by Prussian instructors and was supplied with Prussian materiel and severely modernised, making India a serious military power of the 20th century. In return, Prussia was allowed to build a military port near Bombay, and station the so-called "Indikflotte" ("Indian Ocean Fleet") there. During World War II Prussia stationed other units in India as well, including fighter wings and multiple infantry and armoured units.
Prussia also severely industrialised India (in an "amazingly short amount of time") and was largely responsible for making it an economic world power. India allowed Prussian companies in India, including multiple military shipyards and arms factories (which also produced for the Indian military).
All this served to make India and Prussia very close allies, with India eventually becoming one of Prussia's five closest allies (the only closer ones being Germany, Japan, and Sweden). It did, however, greatly strain Anglo-Prussian relations.
India became an additional, special member of the "Fünf-Mächte-Pakt" ("Five-Powers-Pact") shortly after its formation.

Romanian Civil War

Thanks to Prussian military support, the Iron Guard managed to overthrow the Romanian government and monarchy in the Romanian Civil War of 1935. Following this conflict, Corneliu Codreanu became Romania's leader. In the following years, Romania became a fervent supporter of Prussia and Germany, allying itself with Germany at the start of World War II in 1939.

Corneliu Codreanu; circa 1936

Spanish Civil War

During the Spanish Civil War from 1936 to 1938 Prussia officially stayed neutral. However, in secret it granted various forms of aid and military support to Spain - all in support of the Nationalist faction. It included the formation of the "Legion Adler" (under the command of Prince Rupprecht of Bavaria) as a land and air force, similar to the German "Legion Condor". Both Legions worked together on multiple occasions. One of the most famous soldiers of the Legion Adler was Eugen von Richter, who achieved 23 aerial victories during his time in Spain.
The training the Legion provided to the Nationalists proved as valuable, if not more so, than direct actions. About 15,000 Nationalist soldiers were trained by various Prussian detachments in Spain, who were technically proficient; these covered infantry, tanks and anti-tank units, air and anti-aircraft forces. A total of 9,050 Prussian citizens fought mostly as pilots, ground crew, artillery men, in tanks, and as military advisers and instructors. 95 were killed or missed in action. Prussian aid to the Nationalists amounted to approximately $100,000,000 in 1939 prices. This was broken down in expenditure to: 16.5% used for salaries and expenses, 28% used for direct delivery of supplies to Spain, and 55.5% expended on the Legion Adler.
Following the civil war, Prussia supplied Spain with all kinds of materiel, including tanks, aircraft and firearms.

Prussian officer instructing Nationalist troops of the "Bataillon 'Isolde'"; circa 5 January 1937

Soldiers of the Legion Adler in Spain; circa August 1938

Turkish Civil War

Prussia and its military were also heavily involved in the Turkish Civil War of 1936/37 and helped the fascist faction under Atatürk win, effectively restoring the Ottoman Empire under fascist rule; the Turkish state was renamed the "Turkish Empire". Ever since this conflict, Turkey had been a close ally of Prussia, leading into its membership of the Fünf-Mächte-Pakt of 1939.

Other relations

Since its founding, Prussia had had close ties to Sweden, especially to the royal family, which had helped establish it in the first place. Therefore it was never surprising that Sweden and Prussia had always protected and supported eachother. The armed forces of Prussia and Sweden worked closely together since the former's inception. Prussia played an instrumental role in "militarising" Sweden and improving its industry, making it a serious military and economic power of the 20th century.

Prussia developed good relations to Italy starting in the 1930s, the decade of Benito Mussolini becoming Duce. These relations were strained by the February Putsch in Austria and the annexation of Austria by Germany (see above), but proved strong enough to stay favourable.

Prussian relations with Japan became very close in the 1920s, with multiple joint economic and military programs and projects being accomplished. The "Kaiser Visit of 1923" is often seen as the starting point of the Prussian-Japanese alliance and friendship.
By the 1930s, Japan had become Prussia's second-closest ally, second only to national-socialist Germany (though the Japanese insist to this day that Japan always was Prussia's best and closest ally). Outside observers noted multiple times that the Prussian-Japanese alliance was "quite strange" and that it "developed unnaturally fast".
The military alliance between the two states, consolidated under the Prussian-Japanese Military Assistance and Cooperation Treaty of 1930, eventually went so far that Prussia was allowed to station a rather large fleet, the "Pazifikflotte" ("Pacific Fleet"), in Japan and Japanese-occupied China (mainly in the Prussian military ports in / of Hakodate and Tsingtau [the latter now part of the Special Territory of Kiautschou]). In return, Japan was allowed to station a naval force in Prussian waters (the so-called "European" or "Atlantic Squadron", which successfully fought against the Royal Navy during World War II and closely worked together with the Kriegsmarine).
Also, Prussian companies were allowed in Japan (and vice versa), including arms manufacturers.

Relations between Prussia and the Soviet Union had always been tense; provocations from both sides were not unusual. Prussia had adopted an extremely anti-communist (and anti-leftist in general) stance, with the rare communist sympathisers in Prussia being systematically executed. Prussia even possessed a special "ministry-style" government organisation for the "fight against communism", called the "Antibolschewistische Liga" ("Anti-Bolshevist League"), which was responsible for fighting marxism, communism and other forms of "leftism" in Prussia and Germany, but also conducted both "legal attacks" (e.g. propaganda campaigns) and acts of sabotage, terrorism, etc. on the Soviet Union and its supporters. Prussia also steadfastly refused to maintain an embassy in the Soviet Union and likewise did not allow the Soviets an embassy in Prussia, claiming that the Soviet Union was not a "legitimate state", but a "Jew-led, genocidal, criminal organisation"; as such, Prussia also continually frustrated/obstructed Soviet ambitions and foreign relations.
After the stationing of Soviet soldiers in Lithuania, border conflicts between Prussian and Soviet soldiers became increasingly common, with casualties on each side.

Propaganda poster of the Antibolschewistische Liga; circa 1927. The text reads: "Bolshevism brings war, unemployment, and starvation".

Relations between Prussia and France and the United Kingdom had always been rather "chilly", as the Prussian populace rather disliked the "architects of Versailles".

Prussia supported many fascist and national-socialist movements in Europe, including the "British Union of Fascists", which reached a huge popularity in pre-war Britain (due in no small part to Prussia's support) and would later (in 1946) form the new British government. Prussia also obviously had a strong national socialist party and national socialist organisations itself.

Prussia initially had favourable relations with the USA, though mostly militarily. This can for example be seen with the "Marine Mission", under which troops from the United States Marine Corps trained the "Kaiserliches Marinesoldatenkorps" (KMsk) (which basically is the Prussian/German equivalent of the USMC and fulfills similar duties and tasks) from 1933 to 1939. The KMsk became famous during World War II and fought against the USMC on numerous occasions.
Later, when the Lend-Lease-Act was enacted, Prussia was among the countries that received support from the USA (despite Prussia's alliance with Japan; due to the Allies considering Prussia to be a tactical location in need of defense, in case Germany should try to invade it). It should be noted here that Prussia did not request help, but received it regardless (though there is evidence suggesting that Prussia manipulated events to receive aid). The Lend-Lease support for Prussia ended after the "Great Affront" (see further below).

The Fünf-Mächte-Pakt

In 1939, Prussia entered the so-called "Fünf-Mächte-Pakt" ("Five-Powers-Pact") (FMP for short), an alliance between the states of Prussia, Sweden, Spain, Portugal, and Turkey. The pact was a close military and economic alliance.
When World War II broke out, the FMP distanced itself from both sides, and later from the USA and the USSR as well, maintaining a policy of neutrality.
Attempts from both the Allies and the Axis to convince the FMP to take a side failed - until 1944.

When Germany invaded Poland in 1939, Prussia remained silent, neither condemning nor approving the invasion.

When Britain and France declared war against Germany, Prussia (officially) stayed neutral and revoked the Treaty of Bonn (and with it its alliance with Germany), but continued to (secretly) supply Germany with materials, weapons, etc. This enabled Germany to produce more vehicles, planes, weapons, etc. of high quality to equip its troops with.
Also from 1939 to 1944 Prussia massively expanded its armed forces and defences, especially coastal and aerial defence.

With the help of recently declassified documents, one is able to deduce why Prussia did not come to its allies' aid immediately: the Kaiser thought the Wehrmacht to be entirely capable of winning the war against Poland and France on its own and both him and Reichskanzler Paul von Lettow-Vorbeck (officially Prince of Lettow-Vorbeck since 1936) assessed the Reichsstreitkräfte as not strong enough to defeat a "second Entente", though they believed this could be rectified with enough preparation. (Post-war historians came to the conclusion that both the Kaiser and Von Lettow-Vorbeck massively overestimated the Allies' military strength and were overly cautious). Nevertheless, in the coming years the Reichsstreitkräfte were severely enlarged and modernized. On the international stage it was claimed that this was a defensive measure against "trigger-happy imperialists", which many at the time assumed to mean Germany.
As is also common knowledge by now, the Kaiser's intentions and plans were known to Adolf Hitler and the highest ranks of the German government. They were not opposed to the Kaiser's decision to stay neutral, as they too did not believe that Prussia's help would be necessary to win the war. They were happy with Prussia continuing to, albeit secretly, supply them with goods, ressources and materiel.

During the Winter War (30 November 1939 – 13 March 1940) Prussia actively supported Finland against the Soviet Union. Prussian support included firearms, ammunition, armoured fighting vehicles and aircraft. Also, the Reichsstreitkräfte established four "volunteer regiments" that were deployed to Finland in December 1939. The volunteer regiments included infantry, pilots and tank crews, as well as snipers and commandos. Prussia also sent its "expert in defensive warfare", Generalleutnant Hieronymus Freiherr von Berent, to Finland. Von Berent was made a general of the Finnish Army by Carl Gustaf Emil Mannerheim and was very successful in defending Finland. It is well documented that Prussian troops played a huge part in "winning" the war. After Finland had made peace with the Soviet Union, a Prussian Militärmission ("military mission") was send to Finland to "train, equip, strengthen and modernise" the Finnish armed forces and was put under the command of General Von Berent.
During the Continuation War (25 June 1941 – 12 August 1944), Prussia once again supported Finland (even sending General Von Berent once more).

Generalleutnant Hieronymus von Berent (middle) during a visit to Karlsbad, Sudetenland; circa 1939

From 1939 to 1944 many Prussian volunteers joined the Wehrmacht. The Prussian government quietly accepted this and even condoned German Waffen-SS recruiters in Prussia.
Amongst the more famous Prussian volunteers were Prince Richard of Hohenzollern, first son of the Kaiser, who took with him a tank division created from Prussian volunteers (the 1. Preußische Panzer-Division) and joined the Wehrmacht on 4 September 1939, Johannes von Hohenzollern, who "defected" from the Reichsstreitkräfte in 1939 and joined the Kriegsmarine, Prussia's "Star fighter ace" Eugen von Richter, and Crown Prince Richard's sons Friedhelm and Alfred, who joined the Luftwaffe in February 1940.

Prussian volunteers swearing their allegiance to Hitler; 18 January 1940

Helmzeichen (helmet decal) of Prussian volunteers in service of the Wehrmacht

In addition to volunteers, Prussia provided "Stille Hilfe" ("Silent Help") to the German Luftwaffe, protecting German aircraft in Prussian airspace from pursuers and repairing German aicraft forced to land on Prussian soil.

Worsened relations with the Allies / The Invasion of Denmark and Norway and the Great Affront

Invasions of Denmark and Norway

On 12 January 1940, the Reichsstreitkräfte invaded and occupied Denmark; the Danish Armed Forces surrendered on 13 January. No official explanations were given for the invasion. On the same day, Swedish troops invaded and occupied Norway, supported by the Prussian Luftstreitkräfte. There was no official resistance by the Norwegian Armed Forces and like the Prussia invasion of Denmark, no official explanations were given.
The invasions caused international uproar, but as Britain and France did not want to risk the Five-Powers-Pact joining the war on Germany's side, there were no serious repercussions.

As is now known, the invasions (as was immediately alleged internationally) were conducted in order to secure Prussian and German access to the sea and to prevent Denmark and Norway from supporting or even joining the Allies.

German battleship Tirpitz and German destroyers passing through Norwegian waters; circa 1941

Following the invasions, relations between Prussia and Britain gradually became "worse than terrible" (according to the Prussian newspaper "Die Wahrheit"), with the British committing numerous "affronts" against the Prussians. The Prussian embassy in London was closed (officially for "security concerns") in early 1941, the British embassy in Prussia shut down at the same time.
Adding to the terrible Anglo-Prussian relations was the surge of "Kriegswünscher" (literally "war wishers", a derogatory term for those that wanted Prussia to join the Second World War) in Prussia. From the beginning of the Second World War both the Prussian populace and military were split over wether to join the war or not; British behaviour "hardened the fronts", and in the end, any chance there was (as slim as it might have been) of Prussia joining the Allies had been destroyed. Instead, the wish of joining the Axis became stronger and stronger, the calls for war against the "perfidious Albion" louder and louder.

From 1940 to 1944 the Prussian navy and air force conducted so-called "neutrality patrols" in the Atlantic; Prussian forces in the Atlantic regularly disrupted both German and British operations.

The Prussian Lend-Lease-Programme

In response to the American "Lend-Lease Act", which in the eyes of the Prussian government constituted an act of war, Prussia started the so-called "Leih- und Pacht-Programm für die Achsenmächte" (LPPA, "Lend-Lease-Programme for the Axis Powers") in June 1941 (partly out of spite, as the British press noted). Under this program Prussia supplied Germany, Japan, Italy, Romania, and other Axis nations with materiel between June 1941 and March 1947 (partly in secret). A total of 10 billion PM (Preußische Mark) (roughly equals $52.4 billion in 1942 prices) worth of supplies were shipped. The terms of the agreement provided that the materiel was to be used until time for their return or destruction, but in practice very little equipment was returned. The program was an immense provocation on Prussia's part, almost leading to war. It was officially discontinued (but secretely continued and even extended) after the Allies had demanded as such in December 1941, when the USA joined the war. It was officially continued after the Great Affront (3 May 1943), further leading to alienation between Prussia and the Allies.

Hermann Göring and Adolf Hitler shortly after the negotiations of the LPPA, Schwerin Castle, city of Schwerin; 6 June 1941

Grenzkonflikt '41

When the Wehrmacht started "Unternehmen Barbarossa", beginning on 22 June 1941, troops of the Prussian Zweite Armeeabteilung ("Second Army Section") stationed in East Prussia, under the command of Generaloberst Steffen von Karnberg, joined the Wehrmacht and started their own offensive against the Soviet Union. This offensive, named Mittagsübung ("midday exercise"), was conducted as it had been detailed in the 1940 "Plan Janus". This plan had been created in preparation for war against the Soviet Union, which the leadership of the Prussian army had deemed "inevitable". The Prussian offensive was highly successful, but was stopped under the Hohe Kabinetts Order 'M-201' on 8 July 1941. General Von Karnberg obeyed the order, but instructed his men to leave part of their equipment and supplies behind for the Wehrmacht to use; this included firearms, tanks, aircraft, etc. In addition, not few Prussian soldiers participating in the offensive deserted to the Wehrmacht, perceiving the fight against the Soviet Union "as their duty as German soldiers".
General Von Karnberg was not punished or reprimanded for his actions. In fact, he was awarded the prestigious Pour le Mérite for his success.
Following this conflict, cynically named Grenzkonflikt '41 ("Border conflict 41"), Prussia was officially at war with the Soviet Union. However, Reichskanzler Von Lettow-Vorbeck managed to convince the Prussian military leadership and government to stop any offensive actions. This lead to a situtation similar to the "Phoney War" in 1939/1940 (a phase early in World War II that was marked by a lack of major military operations by the Allies against Germany). Eventually, an unsteady truce was negotiated with help from British and American diplomats, which became active on 1 November 1941.
In Prussia the period of time from November 1941 to June 1944 was often called "Scheinfriede" ("phoney peace"); the Prussian populace and military were intensely displeased with the decision to stop fighting. The German military and government were not happy with this either, as they wished Prussia to fully commit to their cause. In fact, German propaganda repeatedly attacked Reichskanzler Von Lettow-Vorbeck, calling him "der große Zauderer" ("the great procrastinator"). (The Germans did not take active action against him, however, as Prussia still clandestinely supported Germany quite extensively; additionally, Prussian forces were continually engaged in acts of sabotage against the Soviet Union, e.g. the sinking of the Soviet carrier Pervoye Maya by Prussian combat divers.)

Generaloberst Steffen von Karnberg; circa July 1939, during a parade in Germany

The Great Affront

On 26 April 1943 the Allies held a meeting in the Irish city of Galway, which came to be known as the "Conference of Galway"; this was one of the very few Allied meetings Kaiser Friedrich attended. The main goal of the conference was to change the Kaiser's mind about Prussia "hindering Allied efforts". When Chuchill and Roosevelt (Stalin did not attend the conference) demanded from him to allow Allied bombers to pass Prussian airspace (mainly to bomb Berlin), the Kaiser stormed out of the conference in anger after exclaiming that all non-Prussian and non-German aircraft flying over Prussia would be considered as "violating Prussia's airspace" and would be shot down without warning.

30 May 1943. Despite Kaiser Friedrich having clearly stated that he would under no circumstances allow it, the Allies flew their first major attack against the German capital through Prussian airspace, considering the Kaiser's threat an empty one. The Allied attack force consisted mostly of British Avro Lancaster and Handley Page Halifax, American Boeing B-17 and Consolidated B-24 bombers, with North American P-51 Mustangs acting as escort fighters. The Allied force was intercepted by Prussian fighters from the elite Jagdgeschwader I 'Richthofen' and II 'Udet' (JG I and II) and interceptors from the Abfanggeschwader I 'Boelcke' (AG I) and the Schutzgruppe Vedrine (SGV). JG I and JG II were equipped with Albatros D.XIV "Walküre" fighters and Fokker D.XI "Phönix" turbojet fighters; AG I and SVG were equipped with the Hansa-Brandenburg F.I "Komet" heavy fighter and the new AEG K.I "Falke" turbojet interceptor.
The Allies were caught off guard, while the Prussian air force had plenty of time to prepare its attack; this was thanks to early warning from the light cruiser KMS Königsberg, which had been conducting an air surveillance exercise in the Atlantic at the time. The Allied troops lost hundreds of their aircraft, while the Prussian force lost only ten (one of which was damaged in an accident) and did not suffer any casualties.
The battle became known as the "May Incident" and (mainly in Prussia) the "Great Affront" and was perceived as a "slap in the face" by the Prussians; it is often cited as one of the two most important reasons of Prussia entering the Second World War (the other being the Borussia Disaster).
In the aftermath of the battle the already stressed American-Prussian and Anglo-Prussian relations worsened severely and a declaration of war could be avoided only "at the last minute". Following the incident, Prussia boycotted Allied goods and almost completely severed all economic and diplomatic ties; embassies were shut down, bank accounts frozen, Allied citizens and officials expelled from Prussia etc. Another effect of the incident was the rapid spread of strong anti-Americanism throughout and the strengthening of already strong anti-English sentiment in Prussia. Despite this, the Allies continued their Appeasement policy (mainly championed by the USA), trying their best to keep Prussia out of the war.

KMS Königsberg; circa June 1943

A Boeing B-17 that had been forced to land on Prussian soil during the May Incident; circa May 1943. Note the Balkenkreuz on the side, which was painted on the B-17 before it was flown for testing purposes.

In the time from May 1943 to June 1944 the relations between Prussia and the Allies gradually became even worse. One of the peaks of this so-called "Prussian Crisis" was the "Rebellion of the Prussian Pacific Fleet", during which a large part of the Prussian Pacific Fleet defected from the Prussian navy and joined the Imperial Japanese Navy. (This included several capital ships and their crews.) The Allies immediately cast suspicion on the incident, as the Prussian navy was generally known to be highly loyal and had never rebelled before. Indeed, by 1944 Allied investigators had generally come to the conclusion that the so-called "rebellion" was nothing but a ruse and the Prussian ships involved were actually "lent" to the Japanese. (They were proven right after Prussia had entered the war.)
Also, the German government intensified its efforts to "get Prussia to join the war, sensing that the time was right" (quotation from German foreign minister Joachim von Ribbentrop). This included, but was not limited to, German "war celebrities" (e.g. generals, flying aces) visiting Prussia on "diplomatic missions" and increased "propaganda efforts" (e.g. radio programms, movies, etc).
The Japanese Empire and many other Axis nations also intensified their efforts to make Prussia join the war.

Famous German flying ace Walter Nowotny giving autographs to Prussian women; circa November 1943

Japanese propaganda poster put up in a Prussian city circa August 1943. It depicts a Japanese samurai smashing the British navy; depicted behind him are the flags of Germany, Japan and Italy. The lower part of the poster, not visible here, read "Join us in victory!"

Lieutenant general Otani Osamu and other Japanese officers during a visit to Jagdgeschwader I; 12 September 1943

The Borussia Disaster

On 10 May 1944 the Prussian cruise liner SS Borussia was torpedoed by multiple British submarines during her maiden voyage (which was a highly anticipated and very well-attended event) and sunk in the North Sea. This occured despite the British having been explicitly informed about Borussia's route multiple times; in fact, it is alleged (though it has never been proven) that the British intentionally attacked the cruise liner. Borussia's escort, the destroyer KMS GZ 10 Hagen, had spotted and identified, but not intercepted the British submarines due to believing that they posed no threat. Hagen was also sunk; she suffered heavy damage from multiple torpedo hits and sunk with almost all of her crew shortly after Borussia, despite the best efforts of her crew to save both their ship and Borussia's passengers.
Post-war investigation revealed that the British submarines had mistaken the Prussian ships for German ones.
Only 418 of the passengers and crew on board the Borussia (3,821) survived. They were rescued in a heartwarming and intrepid joint rescue effort by aircraft from the Prussian, German and Swedish air forces, ships from the Prussian Navy (including the battleship KMS Kaiserin), the German battleships Scharnhorst and Gneisenau and their escorts, the German submarines U 318, U 324 and U 2502, ships from the Japanese Atlantic Squadron (including the battleship Akagi - popularly referred to as the "Red Empress" by Prussian and German sailors), ships of the Swedish Navy, and multiple Prussian, German, and Swedish merchantmen and civilian vessels.
Among Borussia's passengers were quite a few famous, prominent and important people (most of them Prussians), including:

(A † designates a person that died during the disaster.)
- Alfons Simonius-Stähelin (famous Prussian businessman with Swiss origin who had also been a passenger of the RMS Titanic);
- Theo Weissman (†) (famous actor known from such famous movies as "Der Große Kaiser" and "Die Heroen von Langemarck");
- Bernhardt Trossner (famous Prussian composer);
- Rosalie "Rosi" Jung (popular Prussian singer, later well-known for the songs "In einem blauen Grab", "England brennt" and "Rache ist süß, meine Herren");
- Mathilde von Ysen (†) (daughter of Sigmund von Marienthal) and her husband Wolf (†) (a German SS-Brigadeführer) (their son Thor would go on to become a feared "submarine hunter" and fighter ace);
- Jochen von Hoss (†) (Oberst and renowned Prussian fighter ace and officer, he had achieved multiple aerial victories during the Prussian-Polish War and the Spanish Civil War);
- Melchior von Arnim (German ambassador in Prussia);
- Nagakura Arinaga (Japanese ambassador in Prussia);
- Vijay Bose (†) (Indian ambassador in Prussia);
- Baltasar del Castañón (†) (Spanish ambassador in Prussia);
- Estêvão de Lacerda (†) (Portuguese ambassador in Prussia);
- Gustaf Armfelt (†) (Swedish ambassador in Prussia);
- Duchess Viktoria Luise of Brunswick [née Princess of Prussia] (younger sister of Kaiser Friedrich; one of the Kaiser's most trusted confidents and one of Prussia's "founding mothers");
- Prince Oskar of Hohenzollern (†) (second youngest brother of Kaiser Friedrich; one of the Prussian Empire's "founding fathers" and mayor of the city of Königsberg from 1926 until his death);
- Princess Anna of Hohenzollern-Oldenburg (youngest sister of Kaiser Friedrich; one of the Kaiser's most trusted confidents and one of Prussia's "founding mothers");
- Princesses Emerentia (†) and Margarethe (†) of Hohenzollern (daughters of Prince Albert of Hohenzollern and thereby granddaughters of Kaiser Friedrich);
- Prince Rudolf of Saxony (†) and Prince Heinrich of Saxony (†) (husband and firstborn son of Princess Ophelia of Saxony, herself a niece of Kaiser Friedrich);
- Director of the Reichssicherheit Areus von Bühl (†);
- Reichsminister of Foreign Affairs Archduke Maximilian Eugen of Austria (†);
- Reichsminister of the Interior Duke Ernst August of Brunswick (†);
- Reichsminister of Science Theodor von Gauß (†);
- Reichsminister of Justice Duke Albrecht Eugen of Württemberg (†);
- Reichsminister and Chairman of the Anti-Bolshevist League Eduard von Stadtler;
- Reichsminister of Intra-German Relations Duke Joachim Ernst of Anhalt (†);
- Reichsminister and Chairman of the Defence Council Generalleutnant Prince Rupprecht of Bavaria;
- Reichsminister of War Generaloberst Roman Count of Seitershof;
- Reichsminister of Culture Margrave Friedrich Christian of Meißen (†);
- Reichsminister of Education Prince Ernst Leopold of Lippe;
- Reichsminister for Labour Grand Duke Nikolaus of Oldenburg (†);
- Reichsminister of Social Affairs Margrave Berthold of Baden (†);
- Reichsminister for Transport Anders Prince of Hardenberg (†);
- Reichsminister of Finance Prince Ernst of Saxe-Altenburg (†);
- Reichskanzler (Chancellor of Prussia) Paul Prince of Lettow-Vorbeck (†) (head of Prussia's government - not head of state, that position / authority was held by the Kaiser).

Borussia's sinking caused gigantic outrage in the Prussian populace, and without Reichskanzler Von Lettow-Vorbeck's moderation (that had stopped Prussia from entering World War II multiple times before) and with many of Prussia's most important and influential politicians and officials dead (leaving the government in shock), "a wave of hate for the British, and by extension the other Allies, swept through Prussia, firmly paving the way for war" (quotation from the book "Why Prussia entered the Second World War", by Australian historian A. Hastings). The sinking of the cruise liner and its aftermath are commonly known as the "Borussia Disaster".
The Disaster additionally caused tensions between the Allies and Spain, Portugal, India and Sweden, due to the deaths of their ambassadors in Prussia.
Also following the disaster, martial law was declared and the Prussian government was superseded by a military emergency government instituted by the Kaiser (this government was in power until 1948). All titles, authority and privileges of the Reichskanzler were (temporarily) transferred to the Kaiser.
Vice admiral Siegfried Lech, responsible for the protection of Prussian civilian ships, blamed himself for the disaster and commited suicide on 16 May, despite having been found "definitely not responsible" of the Borussia's demise by a Prussian military court.
For Germany and the Axis the Borussia Disaster turned into a major propaganda coup; their propaganda now found more willing listeners than ever before, especially in Prussia and other neural countries.

Maiden voyage of the Borussia; 10 May 1944