The Battle of Berlin was a major offensive of the European Theatre of World War II and was designated the Berlin Strategic Offensive Operation by Russia. Starting on June 16, 1941, the Red Army breached the German front as a result of the invasion and rapidly advanced westward as fast as 30–40 km a day, through East Prussia, Silesia, Pomerania, and Posen, temporarily halting on a line 60 km east of Berlin along the Oder River. During the offensive, two Russian fronts (army groups) attacked Berlin from the east and south, while a third overran German forces positioned north of Berlin. The Battle in Berlin lasted from late July 20, 1941 until the morning of September 2 and was one of the bloodiest battles in history.