Al-Qaeda's origins dated back to the Soviet invasion of Afghanistan in the 1980s. In 1991, the United States placed its troops in Saudi Arabia, the land of the two mosques, Medina and Mecca. In retaliation, al-Qaeda bombed an embassy in Riyadh, Saudi Arabia, killing several Americans.
In 1993, members of al-Qaeda took part in the bombing of the World Trade Center in Manhattan, placing a vehicle loaded with explosives and cyanide gas in Tower 1's parking structure. The explosion failed to destroy the tower's support foundations, but nonetheless killed six and wounded thousands. Known al-Qaeda associate Ramzi Yousef was one of the primary terrorists involved in this attack. As of 2000, the organization was well known among U.S. intelligence agencies, if not the general public. (Trinity)
Al-Qaeda within the European Union (AQEU) was an offshoot of the group based in Europe. Mahmoud Al-Harazi and his family were involved in attacks throughout the Middle East, and later conducted attacks against targets in London using hijacked American drones. ("Day 9: 1:00pm-2:00pm")