The Battle of Königsberg, also known as the Königsberg offensive, was one of the last operations of the East Prussian offensive during World War II. In four days of urban warfare, Soviet forces of the 1st Baltic Front and the 3rd Belorussian Front captured the city of Königsberg, present day Kaliningrad, Russia. The siege started in late January 1945 when the Soviets initially surrounded the city. Heavy fighting took place for control of overland connection between Königsberg and the port of Pillau, however by March 1945 Königsberg was hundreds of kilometres behind the main front line in the eastern front. The battle ended when the German garrison surrendered to the Soviets on 9 April after a three-day assault made their position untenable. Beginning The East Prussian offensive was planned by the Soviet Stavka to prevent flank attacks on the armies rushing towards Berlin. Indeed, East Prussia held numerous troops that could be used for this. During initial Stavka planning, Joseph Stalin ordered Marshal Konstantin Rokossovsky to annihilate the Wehrmacht forces trapped there. On 13 January 1945, almost 1,500,000 troops supported by several thousand tanks and aircraft of the 3rd Belorussian Front (11th Guards, 39th, 43rd, 50th, 1st Air, 3rd Air, 4th Air, and 15th Air Armies) entered East Prussia, which had been transformed into a gigantic web of fortifications, defensive lines and minefields. Progress was initially very slow. Red Army troops only advanced 1.5 kilometers the first day, through only three defensive lines. In five days, taking heavy losses, Soviet troops advanced only 20 kilometers and were unable to break through German lines into open ground. The initial setback did not last and on 24 January Soviet advance forces reached the shores of the Vistula Lagoon (part of the Baltic Sea), cutting off the German forces in East Prussia from a direct connection with Germany, forcing the Germans to supply the surrounded forces by sea. This operation was accomplished by the 1st Baltic Front under the command of General Hovhannes Bagramyan, also known as Ivan Bagramyan. Encirclement On 25 January 1945, in a tacit acknowledgement that German forces in East Prussia and the Courland Pocket were far behind the new front line, Hitler renamed three army groups. Army Group North became Army Group Courland; Army Group Centre (the army group surrounded in the Königsberg pocket) became Army Group North and Army Group A became Army Group Centre. Those forces, now