The 'Battle of Poznań' was the Soviet capture of the stronghold city of Poznań (Posen in German) in German-occupied Poland after almost a whole month of slow reduction of German fortified positions, intense urban combat, and a final assault on the city’s citadel (24 January 23 February 1945).

Poznań lies in the western part of Poland, which had been annexed by Germany following its 'Weiss' (i) invasion of Poland in 1939, and was the chief city of Reichsgau Wartheland.

By 1945, Soviet advances on the Eastern Front had driven the German forces out of eastern Poland as far to the west as the Vistula river, and rom this line the Soviets launched their 'Vistula-Oder Strategic Offensive Operation' on 12 January, inflicting a huge defeat on the defending German forces of Reichsführer-SS Heinrich Himmler’s Heeresgruppe 'Weichsel' in the north and Generaloberst Josef Harpe’s (from 17 January Generaloberst Ferdinand Schörner’s) Heeresgruppe 'A' in the south, and advanced rapidly into western Poland and eastern Germany.

Some of the cities which lay on the path of the Soviet advance were declared by Adolf Hitler to be Festungen (fortresses) whose garrisons were ordered to mount last-ditch stands. Hitler hoped the Festung cities would hold out behind Soviet lines and thus be in the position to hinder the Soviets through interference with their movement of supplies and their lines of communication. Poznań was declared a Festung in January. The city was held by some 40,000 German troops drawn from a great variety of branches, formations units including the Volkssturm, Luftwaffe ground units, police unit, and highly motivated officer candidates. Facing them were the experienced guards infantry troops of General Polkovnik Vasili I. Chuikov’s 8^th Guards Army and, to a more limited extent, the similarly experienced guards armoured troops of General Polkovnik Mikhail Ye. Katukov’s 1^st Guards Tank Army..

The defenders made use of some of the Festung 'Posen''s existing fortifications built during the period of Prussian rule in the 19^th century. The Fort Winiary citadel stood on a hill to the north of the city centre, and around the city’s perimeter were 18 massively-built forts, spaced at intervals of about 1.25 miles (2 km) in a ring with a radius of about 3.1 miles (5 km).

Poznań lies on the main route between Warsaw and Berlin, and in German hands was a major obstacle to any Soviet operation against the German capital. The Soviet forces had therefore to clear the city of German troops before the final strategic assaults designed to capture Berlin and end the war could begin.

On 21 January, the 1^st Guards Tank Army forced a crossing of the Warta river to the north of the city, but by 24 January these bridgeheads had been abandoned in favour of better bridgeheads to the south of Poznań. Meanwhile, Soviet tank units swept round the city to the north and south, in the process destroying or capturing hundreds of German aircraft. Moving farther to the west, the Soviet armoured formations and units left the capture of the city to Soviet infantry forces.

By 25 January, the 8^th Guards Army had arrived and began a systematic reduction of the Festung. On the following day, two of Poznań's southern forts fell to a swiftly executed assault by the 27^th and 74^th Guards Divisions, and this initial success allowed Chuikov’s troops to penetrate the ring of forts and attack other forts from inside the city’s perimeter.

On 28 January, the Germans relieved Generalmajor Ernst Mattern as the fortress’s commander and replaced him with a dedicated Nazi officer, Generalmajor Ernst Gonell. The latter imposed draconian discipline on the German garrison: in some instances, for example, German troops attempting to surrender were shot by their own side.

Ultimately, the reduction of Festung 'Posen' required the efforts of four divisions from Chuikov’s army and two divisions of General Polkovnik Vladimir Ya. Kolpakchy’s 69^th Army. The 117^th and 312^th Divisions of the 69^th Army’s LXXXXI Corps, the 39^th Guards Division of the 8^th Guards Army’s XXVIII Guards Corps, and on the southern side the 8^th Guards Army’s XXIX Guards Corps (27^th, 74^th and 82^nd Guards Divisions) were arrayed respectively on the northern, eastern and southern sectors of the Festung's perimeter. In the south-western suburb of Junikowo, the XI Guards Tank Corps took up positions to block any German attempt to retreat.

In bitter combat that saw the outlying forts reduced and city blocks seized, the Soviets succeeded in driving the German defenders back toward the city centre and the citadel. By the beginning of February, most of the city had been captured, and by 12 February the Germans held only the imposing citadel.

Gonell had previously believed that other German forces, most notably General Theodor Busse’s 9^th Army, would attack and relieve his besieged forces, but by 15 February he had come to the conclusion that this was not about to happen. Incensed, Gonell ordered his remaining troops to the east of the Warta river to attempt a break-out, and some 2,000 German soldiers managed to infiltrate their way through the Soviet ines and head to the west on the following night.

Deployed against the citadel was the XXIX Guards Corps, with the 27^th Guards Division in the north, the 82^nd Guards Division in the south-west and the 74^th Guards Division in the south-east. The final Soviet assault on the citadel started on 18 February. In this undertaking the Soviet forces faced an old but nonetheless formidable obstacle: a deep ditch matched by a steep rampart on its far side. In an odd echo of mediaeval warfare, the Soviet forces used ladders to cross this obstacle, but then found themselves swept by fire from the citadel’s redoubts. It took most of three days for the Soviets to neutralise these redoubts: one was silenced by flamethrowers and explosives, and the other was rendered ineffective when its lines of fire were blocked by debris thrown in front of the firing ports.

After an assault bridge had been constructed, Soviet tanks and assault guns crossed into the citadel’s main grounds early on 22 February and started the final phase of the struggle for the old fortress. At this point, Gonell gave his troops permission to attempt an escape, but it was too late. Gonell refused to be captured and committed suicide by lying down on a flag and shooting himself in the head.

That evening Mattern, once again in command of the German forces, surrendered the remaining 12,000 troops to Chuikov.

The Germans had held out in Poznań for almost a month, and their possession of the city did serve, in at least a limited way, to complicate and slow Soviet resupply efforts, but other influences had also convinced the Stavka to pause the Soviet forces' advance at the Oder river rather than attempt to push straight on to Berlin in February.

The battle left more than half of Poznań, and nine-tenths of its city centre, severely damaged by artillery fire and the effects of infantry combat. Finally, the outcome of the battle simplified Soviet resupply efforts between Warsaw and the Oder River.

More than 5,000 German troops were killed in the battle, and it has been estimated that the Soviets had lost more than 12,000 men by the battle’s midpoint around 3 February.