Lviv (Polish: Lwów) was a multicultural city just before World War II, with a population of 312,231. The city's 157,490 ethnic Poles constituted just over 50 per cent, with Jews at 32 per cent (99,595) and Ukrainians at 16 per cent (49,747). On 28 September 1939, after the joint Soviet-German invasion, the USSR and Germany signed the German–Soviet Frontier Treaty, which assigned about 200,000 km2 (77,000 sq mi) of Polish territory inhabited by 13.5 million people of all nationalities to the Soviet Union. Lviv was then annexed to the Soviet Union.