During the joint German-Soviet invasion of Poland, which started World War II, on 27 September 1939 the invading Soviet Red Army occupied Chełm, but withdrew two weeks later in accordance with the German-Soviet Frontier Treaty. As early as 7–9 October 1939 the city was occupied by German forces and renamed "Kulm". At the beginning of the war, Chełm's population was around 33,000 of which 15,000 were Jewish. On Friday, 1 December 1939, at 8 o'clock, around 2000 Jewish men were driven at dawn to the market-square ("Okrąglak" or "Rynek") surrounded by the German SS formations and local indigenous officials. They were forced on a death march to Hrubieszów. Hundreds were murdered on the march, others were tortured and beaten. They were marched to the Soviet border where they were forced to cross the river under gunfire. Eventually perhaps 400 of the men survived the Death March and 1600 were slaughtered.