On June 22, 1941, Germany suddenly invaded the Soviet Union, starting the Great Patriotic War of 1941-45. Ukraine was one of the main strategic targets of the Wehrmacht eager to seize the USSR's industrially developed south. Still the Red Army's staunch resistance frustrated Germany's plans. The Battles of Kyiv, Odesa and Sevastopol (these three cities were titled "Hero-cities" after the war) slowed the Nazi offensive. In Ukraine the Nazi occupation regime was marked by special cruelty. In the years of the war its population dropped by 14.5 million. There were more than 200 concentration camps. Hundreds of thousands were put to death at the Yanivka camp in Lviv and in the Babi Yar ravine near Kyiv. Some 250 villages of Ukraine were burned together with their residents.