Operation Bagration was a major Soviet offensive against German Army Group Centre in June 1944, during the Second World War and regarded by Russian historians as perhaps the most decisive operation of the war on the Eastern Front. In the space of four weeks, the Soviets destroyed 25 German divisions, crossed eastern Poland, and advanced 725 km/ finishing on the line of the Vistula river. The German field marshal Ernst Busch was forewarned of the attack and requested permission to fall back to a better defensive line on the river Beresina, but Hitler refused and ordered the Group to remain in position. The Soviet force consisted of over 40 tank brigades plus supporting troops, heavily outnumbering the Germans in both tanks and artillery. The Germans were encircled and cut off in the Vitebsk, Mogilev, and Bobruysk areas and suffered heavy losses. Research Operation Bagration