Abdullah Yusuf Azzam was a Palestinian jihadist and theologian. Belonging to the Salafi movement within Sunni Islam, he and his family fled from what had been the Jordanian-annexed West Bank after the 1967 Arab–Israeli War and pursued higher education in Jordan and Egypt before relocating to Saudi Arabia. In 1979, Azzam issued a fatwa advocating for "defensive jihad" in light of the outbreak of the Soviet–Afghan War, and subsequently moved to Pakistan to support the Afghan mujahideen.

Mohammed Atef was an Egyptian miltant and prominent military chief of al-Qaeda, and a deputy of Osama bin Laden, although Atef's role in the organization was not well known by intelligence agencies for years. He was killed in a US airstrike in November 2001.