The 'Battle of the Oder-Neisse' was the name given by the Germans to the the first phase of one of the last two strategic offensives undertaken by the Soviet forces in the central European campaign of 1 January/9 May 1945 (April 1945).

The battle’s initial breakthrough phase was fought over a period of four days from 16 to 19 April within the larger context of the 'Battle of Berlin'. The Soviet military planners divide the frontal and pincer phases of the operation, named as the 'Berlin Strategic Offensive Operation' into the 'Stettin-Rostock Offensive Operation' (16 April/5 May) by the 2^nd Belorussian Front, the 'Seelow-Berlin Offensive Operation' (16/19 April) by the 1^st Belorussian Front, the 'Cottbus-Potsdam Offensive Operation' (16/27 April) by the northern flank and Cavalry Mechanised Group of the 1^st Ukrainian Front, and the 'Spremberg-Torgau Offensive Operation' (16/25) by the southern flank of the 1^st Ukrainian Front.

The battle included heavy fighting by fronts commanded by Marshal Sovetskogo Konstantin K. Rokossovsky (2^nd Belorussian Front), Marshal Sovetskogo Soyuza Georgi K. Zhukov’s 1^st Belorussian Front and Marshal Sovetskogo Soyuza Ivan S. Konev’s 1^st Ukrainian Front. These fell on the German defences of Generaloberst Gotthard Heinrici’s Heeresgruppe 'Weichsel' and Generalfeldmarschall Ferdinand Schörner’s Heeresgruppe 'Mitte'.

Most of the fighting took place during 1^st Belorussian Front’s assault on the Seelow Heights defended by Generalleutnant Theodor Busse’s 9^th Army of Heeresgruppe 'Weichsel', in what became known as the 'Battle of the Seelow Heights'. The 1^st Ukrainian Front encountered much lighter resistance crossing the Neisse to penetrate defensive lines of Heeresgruppe 'Mitte'.

In the early hours on 16 April, the 'Berlin Strategic Offensive Operation' began with a massive bombardment by thousands of artillery pieces and Katyusha rockets in a barrage which continued for as much as two hours on some sectors of the front. Shortly after this, and well before dawn, the 1^st Belorussian Front attacked across the Oder river and the 1^st Ukrainian Front across the Neisse river. The 1^st Belorussian Front was strengthened because it had the more difficult assignment and was facing the majority of the German forces in prepared defences.

The initial attack by the 1^st Belorussian Front was a disaster, for Heinrici had anticipated the move and withdrawn his defenders from the first line of trenches just before the Soviet artillery destroyed these defences. The light of 143 searchlights, which were intended to blind the defenders, was diffused by the early morning mist and made useful silhouettes of the attacking Soviet formations and units. The swampy ground proved to be a great hindrance and under a German counter-barrage the Soviet casualties were very heavy. Frustrated by the slow advance, or perhaps on the direct orders of the Stavka, Zhukov committed his reserves, which in his plan were to have been held back to exploit the expected breakthrough. By a time early in the evening, an advance of almost 3.7 miles (6 km) had been achieved in some areas, but the German lines remained relatively intact.

Zhukov was forced to report that the Seelow Heights offensive was not going as planned. In order to spur Zhukov, Iosef Stalin told him that he would give Konev permission to wheel his tank armies toward Berlin from the south. The Soviet tactic of using a dense concentration of firepower was providing the usual results, but by the fall of night on 17 April the German front before Zhukov remained unbroken, but only just.

On 18 April, both of the Soviet fronts made steady progress, and by nightfall the 1^st Belorussian Front had reached the third and final German line of defence. On 10 April, the fourth day of the battle, the 1^st Belorussian Front broke through the final defence line of the Seelow Heights position with nothing except hard-hit and retreating German formations between it and Berlin. The remnants of Busse’s 9^th Army, which had been holding the heights, and the remaining northern flank of General Fritz-Hubert Gräser’s 4^th Panzerarmee, were in danger of being enveloped by elements of the 1^st Ukrainian Front.

In the south, the attack by the 1^st Ukrainian Front in the 'Cottbus-Potsdam Offensive Operation' was keeping to plan because Schörner’s Heeresgruppe 'Mitte' was not providing as much opposition as that faced by Zhukov’s troops. The 4^th Panzerarmee, on the northern flank of Heeresgruppe 'Mitte', was falling back under the weight of the 1^st Ukrainian Front’s offensive. Two Panzer divisions on the southern flank were retained in reserve for possible need in the centre of the army group’s front, and were thus not available for deployment to shore up the 4^th Panzerarmee. This was the turning point in the battle, because by the fall of night the positions of both Heeresgruppe 'Weichsel and the southern sectors of Heeresgruppe 'Mitte' were becoming untenable. Unless they fell back into line with the 4^th Panzerarmee they faced envelopment. In effect, Konev’s successful attacks on Schörner’s poor defences to the south of the Seelow Heights positions were unhingeing Heinrici’s defence.

On 18 April, the 1^st Ukrainian Front, having seized Forst, was preparing to break out into relatively flat terrain. Elements of the 3^rd Guards, 3^rd and 4^th Guards Tank Armies, which were the 1^st Ukrainian Front’s Cavalry Mechanised Group, had exploited the breach in the 4^th Panzerarmee sector of the front and turned to the north between Seyda and Jüterbog toward a meeting with the 1^st Belorussian Front in the area to the west of Berlin.

In the 'Spremberg-Torgau Offensive Operation', others of the 1^st Ukrainian Front’s southern flank attacked to the west and met US forces on the line of the Elbe river. During the attack Oberst Otto Ernst Remer’s Führerbegleitbrigade was encircled in the Spremberg pocket and destroyed, its survivors who managed to break out surrendering to the Americans. The offensive marked the 'meeting at Torgau' when the 58^th Guards Rifle Division of the 5^th Guards Army, part of 1^st Ukrainian Front, made contact with the 69^th Division of the US 1^st Army near Torgau on the Elbe river.

In the 'Stettin-Rostock Offensive Operation', on 20 April between Stettin and Schwedt, Rokossovsky’s 2^nd Belorussian Front attacked the northern flank of Heeresgruppe 'Weichsel', held by General Hasso-Eccard von Manteuffel’s 3^rd Panzerarmee. By 22 April, the 2^nd Belorussian Front had established a bridgehead, more than 9.3 miles (15 km) deep, on the western bank of the Oder river, and was heavily engaged with the 3^rd Panzerarmee. On 25 April, the 2^nd Belorussian Front broke through the 3^rd Panzerarmee's line around the bridgehead to the south of Stettin and crossed the Randow swamp in the Gramzow area. The Soviet front was now free to move to the west toward the British 21^st Army Group, and north towards the Baltic ports of Stralsund and Rostock.

By the end of 19 April, the German positions on the Eastern Front to the north of Frankfurt an der Oder around the Seelow Heights and to the south around Forst had ceased to exist. The breakthroughs allowed the two Soviet fronts to envelop large parts of the 9^th Army and 4^th Panzerarmee in a large pocket 23 miles (37 km) to the east of Frankfurt an der Oder that attempted to follow the Oder-Spree Canal to Berlin. Attempts by the 9^th Army to break out to the west later resulted in the 'Battle of Halbe'.

While the 1^st Belorussian Front encircled Berlin, the 1^st Ukrainian Front started the battle for the city itself.

The cost to the Soviets in making the initial breakthrough had been very high. Between 1 and 19 April, it lost over 2,807 tanks. During the same period, the Western Allies lost 1,079 tanks.