The 'Warsaw-Poznan Offensive Operation' was the first of the two Soviet offensives fought by Marshal Sovetskogo Soyuza Georgi K. Zhukov’s 1^st Belorussian Front within the 'Vistula-Oder Strategic Offensive Operation' to press the Soviet advance from Warsaw on the axis directly to the west toward Berlin, and including the month-long Battle of Poznań (13 January/23 February 1945).

The other sub-operation of the 'Vistula-Oder Strategic Offensive Operation' was the 'Sandomierz-Silesian Offensive Operation' (12 January/3 February 1945).

The Battle of Poznań (Posen in German) was the Soviet assault on and capture of the stronghold city of Poznań in occupied Poland, and with it the destruction of the German garrison formations. The eventual Soviet victory in this battle needed almost an entire month of costly effort including the reduction of many fortified positions, intense urban combat and at its climax a final assault on the city’s citadel.

Lying on the Warta river, Poznań is located in the western part of Poland which had been annexed by Germany following its 'Weiss' (i) invasion of Poland in September 1939, and was the chief city of the Reichsgau Wartheland.

By mid-January 1945, the forces of the 1^st Belorussian Front (47^th Army, 61^st Army, 5^th Shock Army, 8^th Guards Army, 69^th Army, 33^rd Army, 3^rd Shock Army, 2^nd Guards Tank Army, 1^st Guards Tank Army, Polish 1^st Army, 16^th Air Army, II Guards Cavalry Corps , VII Guards Cavalry Corps, 11^th Tank Army and IX Tank Corps) held the line along the Vistula river between Serock to Józefów, and possessed on its western bank bridgeheads in the areas of Magnuszew and Puławy to the south of Warsaw.

Facing this massive Soviet concentration was General Smilo Freiherr von Lüttwitz’s (from 19 January General Theodor Busse’s 9^th Army of Generaloberst Josef Harpe’s (from 17 January Generaloberst Ferdinand Schörner’s Heeresgruppe 'A', which was redesignated as Heeresgruppe 'Mitte' on 25 January.

The Soviet plan was firstly to dismember the German army group and secondly to destroy it in detail. The main blow was to be delivered from the Magnuszew bridgehead in the direction of Kutno and Poznań by the General Polkovnik Pavel A. Belov’s 61^st Army, General Leytenant Nikolai Ye. Berzarin’s 5^th Shock Army, General Polkovnik Vasili I. Chuikov’s 8^th Guards Army, General Polkovnik Andrei A. Grechko’s 1^st Guards Army, General Leytenant Porfiri G. Chanchibadze’s 2^nd Guards Army and the II Guards Cavalry Corps. In order to provide additional strength for the development of initial success, these forces were then to be supplemented by General Major Nikolai P. Simoniak’s 3^rd Shock Army. Subsidiary attacks were also to be made, this this instance from the Puławy bridgehead, in the direction of Radom and Łódź, by General Leytenant Vladimir Ya. Kolpakchy’s 69^th Army, General Polkovnik Ivan I. Lyudnikov’s 33^rd Army and the VII Guards Cavalry Corps. To the north of Warsaw, General Leytenant Franz I. Perkhorovich’s 47^th Army and General Major Stanislav Poplavsky’s Polish 1^st Army received the task of going over to the offensive four days after the start of the offensive and, in co-operation with Perkhorovich’s 47^th Army, Belov’s 61^st Army and General Major Aleksei I. Radzievsky’s 2^nd Guards Tank Army , destroy the Germans forces in the Warsaw are and take Warsaw, the capital of Poland.

The 'Warsaw-Poznań Offensive Operation' started on 14 January with a surprise attack by the forward battalions in each bridgehead on a front some 60 miles (100 km) wide, and within an hour these units had advanced 1,25 to 1.,85 miles (2 to 3 km) without meeting any form of organised resistance. By the end of the day, the 5^th Shock Army and 8^th Guards Army had advanced as much as 7.5 miles (12 km), and the 61^st Army crossed the Pilica river across the ice and penetrated 1.85 miles (3 km) into the German defences. The 69^th Army, 33^rd Army, IX Tank Corps and XI Tank Corps broke through the German defences to a depth of 12.5 miles (20 km).

On January 15, 1945, the 1^st Guards Tank Army reached the Pilica river, and the XI Tank Corps and IX Tank Corps took the city of Radom by the morning of 15 January. The 47^th Army, going on the offensive on 16 January, threw the Germans back across the Vistula river and forced this river barrier in the area to the north of Warsaw off the march. On the same day, in the zone of the 5^th Shock Army, the 2^nd Guards Tank Army was introduced into the breakthrough and, after a swift advance of 50 miles (80 km), reached the Sochaczew area and cut the lines of retreat by which the German forces in the area of Warsaw might had fallen back to the west.

On 17 January, the 47^th Army and 61^st Army, together with the Polish 1^st Army, took Warsaw.

In the first four days of its offensive, the 1^st Belorussian Front defeated the main forces of the 9^th Army, broke through its defences and advanced between 60 and 80 miles (100 and 130 km). The Soviet ground forces were actively and ably supported by the warplanes of General aviation of General Polkovnik Sergei I. Rudenko’s 16^th Air Army which, among a host of targets, savaged the German strongpoints immediately in front of the advancing ground forces, and troop concentrations and communication centres in the depths of the German defence zone. On the morning of 18 January, the 1^st Belorussian Front began a decisive pursuit of the disintegrating German forces. On 19 January, Soviet forces took Łódź.

By 22 January, Soviet armoured forces had reached the Poznań defence line. On 23 January, elements of the 2^nd Guards Tank Army took the city of Bydgoszcz. Bypassing what was in effect the fortress of Poznań from the south, after the failure of an initial attempt to take this city, whose capture was now entrusted to the infantry forces of the 8^th Guards Army and 69^th Army, the 1^st Guards Tank Army crossed the Warta (Warthe in German) river on 25 January and pressed forward as rapidly as it could to the Oder river.

Before the arrival of the Soviet forces, Poznań had became one of several German and German-held cities and towns which lay on the path of the Soviet advance and were therefore declared by Adolf Hitler to be Festungen (fortresses), whose garrisons were ordered to fight last-ditch stands. Hitler hoped that the designated Festungen could and would hold out behind the front line of the Soviet advance, and thereby be in the position to interfere with the movement of supplies and lines of communication. Poznań was declared a Festung (fortress) during January, and under the local command of the 9^th Army within Heeresgruppe 'Weichsel', was defended by some 84,000 men from a variety of branches including 15,700 men of the garrison, 22,600 regular troops and Luftwaffe field units, 11,600 auxiliaries, 8,000 Volkssturm, 25,000 SS troops and police, highly motivated officer candidates, and 1,100 Hungarian troops and mobilised citizens. Against this miscellany was pitted Chuikov’s experienced 8^th Guards Army, and the Soviet strength was in the order of 105,000 men including 5,000 Polish troops.

The defenders of Poznań exploited some of the surviving parts of the city’s fortifications which had been built during Prussian rule in the 19^th century. The citadel in the village of Winiary stood on a hill to the north of the city centre, and around the perimeter of the city were 18 massive 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 serious obstacle to any Soviet operation against the German capital. So the Soviets had to clear the city of German troops before the start of the final offensive to capture Berlin and end World War II in Europe.

On 21 January General Polkovnik Mikhail Ye. Katukov’s 1^st Guards Tank Army forced a crossing of the Warta river in the area to the north of the city, but by 24 January this formation’s bridgeheads had been abandoned as better bridgeheads were now available in the area to the south of Poznań. Soviet tank formations had meanwhile swept round the north and south of the city, capturing hundreds of German aircraft in the process. Advancing to the west, the Soviet tank formations then left the capture of the city to other Soviet forces.

By 25 January, the 8^th Guards Army had reached Poznań and embarked on a systematic reduction of the fortress. During the second day of the undertaking, two of Poznań's southern forts fell to a hasty assault by the 27^th and 74^th Guards Rifle Divisions, and this early success allowed Chuikov’s troops to penetrate through the ring of forts and attack other forts from inside as well as outside the city.

On 28 January, on the orders of the German high command, Generalmajor Ernst Mattern was replaced as the fortress commander by a dedicated Nazi, Generalmajor Ernst Gonell. Gonell imposed draconian discipline on the German garrison: there were instances in which German troops attempting to surrender were shot by their own side.

Ultimately, the reduction of Festung Posen required the use of six Soviet divisions, four of them from the 8^th Guards Army and two from Kolpakchy’s 69^th Army. The 117^th and 312^th Divisions of the 60^th Army’s LXXXXI Corps were deployed on the eastern side of the city, the 39^th Guards Division of the 8^th Guards Army’s XXVIII Guards Corps on the northern side, and the 27^th, 74^th and 82^nd Guards Divisions of the 8^th Guards Army’s XXIX Guards Corps in the south. In the south-western suburb of Junikowo, the XI Guards Tank Corps blocked the only practicable line of retreat available to the Germans.

In bitter combat that saw the steady reduction of the outlying forts and the seizure of city blocks, the Soviet troops steadily drove the German defenders toward the centre of the city and the citadel. By the beginning of February 1945, most of the city had been captured, and by 12 February, the Germans held only the citadel.

Up to this time Gonell had thought that other German forces would move to the relief of the beleaguered German garrison, but by 15 February it was clear that this was not going to happen. Incensed, he ordered the troops to the east of the Warta river to break out of the Soviet encirclement, and some 2,000 Germans managed to filter through the Soviet perimeter and move to the west during the following night.

By this time the reduction of the citadel was the task of the XXIX Guards Corps, which deployed its 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 for the final assault on the citadel, which began on 18 February. In front of the Soviet assault formations was a deep ditch with a steep rampart on the far side. In an odd echo of mediaeval warfare, the Soviets used ladders to cross this obstacle, but found themselves swept by fire from the defenders in the citadel’s redoubts. It took the Soviet troops almost three days to subdue these redoubts, one of which was silenced by flamethrowers and explosives, while the others' 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 main area of the citadel early on 22 February at the beginning of the final fight for the fortress. It was at this time that Gonell gave permission for his surviving men to attempt an escape, but it was too late. Gonell refused to be captured and committed suicide.

During the evening of the same day, Mattern, once again in command of the German forces, surrendered the remaining 12,000 Germans.

The Germans had held out in Poznań for almost a month in which their possession of the city had complicated the Soviet resupply efforts, but other influences had also convinced the Stavka to pause the Soviet advance at the Oder river instead of attempting to push straight on to Berlin without a pause in February 1945.

The battle left over half of the city and some 90% if its centre savaged by artillery fire and the effects of infantry combat, and the battle’s outcome simplified Soviet resupply efforts between Warsaw and the Oder river.

The Battle of Poznań cost the Soviets about 10,000 casualties and the Poles about 5,000, while the losses of the Germans and their allies were some 6,000 Germans and 100 Hungarians killed, and 23,000 men taken prisoner.

Meanwhile, on 26 January Soviet armoured forces had reached the German/Polish frontier of 1939. On 26 January, the 2^nd Guards Tank Army broke through the 'Pommernwall' defence line off the march. This 'Pommernwall' (Pomeranian wall) was a defensive line built by the Germans in 1944 within Pomerania between the Neustettin (Szczecinek in Polish) and Landberg (Gorzów Wielkopolski in Polish) via Deutsch-Krone (Walcz in Polish) and Kreuz (Krzy Wielkopolski in Polish) on the basis of the Pomeranian fortified area built in 1932/37, as well as the fortress of Schneidemühl (Piła in Polish). The Pomeranian fortified area comprised a large number of well-constructed bunkers and strongpoints echeloned in depth. Its eastern face extended along hills that are high and forested. Soviet forces of the 2^nd Tank Army broke through the Pomeranian defence zone on 28 January, and the surviving German defenders were surrounded in Schneidemühl on 1 February.

Following the 2^nd Tank Army, the 3^rd Shock Army, 5^th Shock Army, 61^st Army, 47^th Army, Polish 1^st Army and II Guards Guards Cavalry Corps completed the breakthrough and continued their assault to the west of the 'Pommernwall'.

On 29 January, the 1^st Guards Tank Army, 8^th Guards Army, 33^rd Army and 69^th Army, broke through the Mezeritsky fortified area and entered Germany. On 31 January, advance units of the 2^nd Guards Tank Army and the 5^th Shock Army reached the Oder river. By the end of 3 February, the forces of the 1^st Belorussian Front’s centre and left wing had cleared the Germans from the right bank of the Oder river some 60 miles (100 km) to the south of Zehden, and seized a bridgehead on the river western bank both north and south of Küstrin.

At this time, the Germans were attempting to concentrate major forces in Pomerania as Heeresgruppe 'Weichsel' under the illusory command of Reichsführer-SS Heinrich Himmler in order to strike to the south into the right flank of the 1^st Belorussian Front. Zhukov countered this German grouping with four combined arms armies, two tank armies and one cavalry corps.

This left Zhukov’s drive on Berlin with four combined-arms armies weakened in previous battles, two tank armies and one cavalry corps. As a result of the threatened German counter-offensive from the north, as well as the backlog of logistical services and the redeployment of air units, the continuation of the Soviet offensive toward Berlin was deemed inexpedient and the Soviet supreme command ordered an end to the offensive.

The 'Warsaw-Poznań Offensive Operation was one of the largest front-line operations carried out during World War II. Having started with a breakthrough in several sectors with a total width of 21 miles (34 km), the 1^st Belorussian Front had by the end of the operation expanded its front to a width of some 310 miles (500 km) and advanced to a depth of 310 miles (500 km), taking the entire western part of Poland. As well as liberating the whose of Poland to the west of the Vistula river, the Soviet forces had also seized a significant bridgehead on the western bank of the Oder river, and this became one of the launch points for the decisive 'Berlin Strategic Offensive Operation'.