According to the Encyclopedia of the Holocaust (Edition 1990, Volume 2, Pages 706 and 707), Mufti Hajj Amin al-Husseini, the Mufti of Jerusalem, made a major contribution to the Nazi war effort by organizing "in record time" Muslim SS units in Croatia. These units were involved in some of the worst atrocities of World War II.
An estimated 20,000 Muslims fought in the Hanjar (Sword) SS Division. Most of their activities were directed against the Yugoslav partisans, led by Josip Broz Tito, and the local Jewish and Romany populations. They also conducted police and security activities in Fascist Hungary. The Nazis recruited two SS divisions from Yugoslavia's Muslim population: the Bosnian 13th Waffen Hanjar (or Handschar) SS division, and the Albanian Skanderbeg 21st Waffen SS division.
According to the Encyclopedia of the Holocaust:
The Mufti of Jerusalem salutes the Bosnian Handschar
From the Encyclopedia of Holocaust, Edition 1990, Vol. 2, page 704. The caption reads: Hajj Amin al-Husseini, Mufti of Jerusalem, inspecting troops in Bosnia (1943).