In 1979, the Soviet Union deployed its 40th Army into Afghanistan, attempting to suppress an Islamic rebellion against an allied Marxist regime in the Afghan Civil War. The conflict, pitting indigenous impoverished Muslims (mujahideen) against an anti-religious superpower, galvanized thousands of Muslims around the world to send aid and sometimes to go themselves to fight for their faith. Leading this pan-Islamic effort was Palestinian sheikh Abdullah Yusuf Azzam. While the military effectiveness of these "Afghan Arabs" was marginal, an estimated 16,000 to 35,000 Muslim volunteers came from around the world came to fight in Afghanistan.