Al-Qaeda ('The Base') is a militant Sunni Islamist organization founded by Osama bin Laden in the late 1980s.

It originated among the foreign Arab fighters (mujahideen) who had fought against the Soviet Union in Afghanistan.

Al-Qaeda's ideology calls for a global jihad to oppose Western influence in Muslim lands and establish a pan-Islamic caliphate.

Before 2001, Al-Qaeda was responsible for several major attacks, including the 1998 bombings of U.S. embassies in Kenya and Tanzania.

On September 11, 2001, Al-Qaeda launched its most devastating attack against the United States.

Nineteen Al-Qaeda terrorists hijacked four commercial airliners.

Two planes were flown into the Twin Towers of the World Trade Center in New York City, causing both towers to collapse.

A third plane was flown into the Pentagon, the headquarters of the U.S. Department of Defense, in Virginia.

The fourth plane, United Flight 93, crashed into a field in Pennsylvania after its passengers and crew fought back against the hijackers.

The 9/11 attacks killed nearly 3,000 people and triggered the U.S.-led global 'War on Terror.'