The 13th Waffen Mountain Division of the SS "Handschar" was a mountain infantry division of the Waffen-SS, an armed branch of the German Nazi Party that served alongside but was never formally part of the Wehrmacht during World War II. From March to December 1944, it fought a counter-insurgency campaign against communist-led Yugoslav Partisan resistance forces in the Independent State of Croatia, a fascist puppet state of Germany that encompassed almost all of modern-day Croatia, all of modern-day Bosnia and Herzegovina as well as parts of Serbia. It was given the title Handschar after a local fighting knife or sword carried by Ottoman policemen during the centuries that the region was part of the Ottoman Empire. It was the first non-Germanic Waffen-SS division, and its formation marked the expansion of the Waffen-SS into a multi-ethnic military force. Composed of Bosnian Muslims with some Catholic Croat soldiers and mostly German and Yugoslav Volksdeutsche officers and non-commissioned officers, it took an oath of allegiance to both Adolf Hitler and the Croatian leader Ante Pavelić.