The Red Army and Polish Army offensive set off from the Vistula river in mid-January 1945. First Ukrainian Front and 1st Belorussian Front units rapidly made their way towards Wielkopolska. Poznań was proclaimed a fortress in late January 1945 and was commanded by Gen. Ernst Mattern (replaced by Gen. Ernst Gonell on 7 February).
The bombs and shells that fell on the historic centre of Poznań during the fighting reduced it to a pile of rubble. When the advance on Poznań failed to take the city, fierce fighting broke out in and around the Old Town and city centre. The battle for the city dragged on until 16 February. Taking the Citadel, the Germans’ last line of resistance, took another week. The 19th-century fortifications effectively resisted successive assaults. Eventually, some 2,000 Poznanians joined the Soviet troops, most of them forcibly mobilised into support units. The battle reached its climax on the night of 22-23 February. Gen. Gonell committed suicide during the final phase and the rest of the German garrison, pushed into the area of the present amphitheatre, raised the white flag in the morning. The Poznań Citadel was taken on 23 February – the anniversary of the creation of the Soviet Army – in line with the Red Army tradition of honouring important days. More than 10,000 Red Army soldiers and around 600 Poznań civilians died in the battle for Poznań in January and February 1945. The casualties in the fight for the Citadel were almost 6,000 and 200 respectively. Some 5,000-6,000 Germans were died. The city suffered heavy damage and was about 55% (80-90% in the Old Town) destroyed.