After the Kingdom of Yugoslavia was invaded by the Axis powers during World War II, all of Bosnia was ceded to the newly created Independent State of Croatia.
[2] ...was a letter sent to Adolf Hitler in the autumn of 1942 by prominent Bosniaks, including the then mayor of Sarajevo, Mustafa Softić, translated and published in Vladimir Dedijer's book "Genocide against Muslims 1942-1945."
[3]Starting in 1941, Yugoslav communists under the leadership of Josip Broz Tito organized their own multi-ethnic resistance group, the partisans, who fought against both Axis and Chetnik forces.
On 29 November 1943 the Anti-Fascist Council of National Liberation of Yugoslavia with Tito at its helm held a founding conference in Jajce where Bosnia and Herzegovina was reestablished as a republic within the Yugoslavian federation in its Ottoman borders.
[1] During the war, and following the massive deterioration of internal security under the incompetent Ustaše regime, the Nazis created a quisling Waffen-SS unit in Bosnia called the 13th Waffen Mountain Division of the SS Handschar (1st Croatian) in February 1943.