After being annexed by Nazi Germany in 1939, Poznań was incorporated into the Third Reich and underwent aggressive Germanisation, with over 100,000 civilians expelled from the city and replaced with Volksdeutch settlers from the Baltic States and other regions. Of those exiled many died in mass executions conducted in 1940 in the area surrounding Lake Rusałka. Under occupation, Poznań’s Imperial Castle was remodelled as a residence for Nazi Governor Arthur Greiser by infamous Reich architect Albert Speer, though Greiser spent most of the war residing at ul. Berwińskiego 5. Gestapo HQ was located in Dom Żołnierza (ul. Niezłomnych 1), which became an interrogation centre with thousands of Poles tortured in the basement. It was stormed by the Red Army in February 1945 and fiercely defended by the SS, who ultimately opted for mass suicide over capture. Completely battered by this siege, the only original remnant of the building is its tower, spared the brunt of Soviet aggression so it could be used as a reference point by artillery units.

Prisoners processed through Dom Żołnierza usually ended up in the (still functioning) prison on ul. Młynska, or the notorious Fort VII in the far west of the city. Used as a penal camp, this network of 19th century fortifications today serves as the Wielkopolska Martyrs Museum, and its gloomy subterranean chambers are filled with relics recovered from the site – photographs, cutlery, wallets and rosaries. Outside, the ‘Death Wall’ commemorates the thousands executed by firing squad.

It was actually in Poznań in 1943 that Himmler declared Nazi intentions to exterminate Jewish life, and today little survives of Poznań’s Jewish heritage, with the early 19th century graveyard on ul. Głogowska destroyed by the Nazis, before being incorporated into the Poznań International Fair complex by communist authorities after the war.

The Soviet siege of Poznań resulted in 90% total destruction of the city’s Old Town, and a few images of the city in ruins can be viewed in the Historical Museum of Poznań inside the Town Hall. Another area defended to the last man was the fortress in Citadel Park just north of the Old Town, which today houses two military museums - the Poznań Army Museum and the Museum of Armaments. In addition to several war monuments, the Citadel Park also hosts a British military cemetery, which is the resting place of Allied airmen shot down over Poland during WWII and also several of those captured during “The Great Escape” - the famous POW escape story popularised by the Hollywood movie with Steve McQueen.