During World War II, German forces begin their siege of Leningrad, a major industrial center and the USSR's second-largest city. The German armies were later joined by Finnish forces that advanced against Leningrad down the Karelian Isthmus. The siege of Leningrad, also known as the 900-Day Siege though it lasted a grueling 872 days, and resulted in the deaths of some one million of the city's civilians and Red Army defenders.