The CIA Counterterrorist Center (CTC) provides a classified briefing to the Senate Select Committee on Intelligence in which it states that some 70,000 to 120,000 people were trained in al Qaeda camps in Afghanistan since the Soviet invasion in 1979.
It is a huge number, but the CIA is unable to precisely answer how many active al Qaeda members there are, nor how many who trained during the Soviet occupation of Afghanistan was mere jihad “tourists” from Saudi Arabia and the Gulf states, with no intention of ever going on to conduct terrorism. The core of al Qaeda fighters – at 9/11 – in fact is thought to be more in the 5,000-6,000 range.