When did WW2 start?

Serbs were victims of an extermination policy of Croat NDH since this Nazi puppet state was formed in 1941. The murders took many forms: burning of live Serbs forced into churches; slaughter of Serbs by small death squads, often numbering only three, called "black threes", who rampaged by night through villages in which dogs were first poisoned. The squads filled foiba pits with still-living Serbs, often connected by barbed wire, and practiced extremely cruel methods of torture and execution such as gouging eyes and cutting salted necks. They also nailed guts of slaughtered victims to the roofs. Extermination in Jasenovac camp existed since its onset in 1941, at the time when Germans had not yet started their systematic genocide, and it has appalled even the SS, though soon enough they were organizing systematic extermination in their camps too.