The simultaneous hijacking of four commercial jets was a bold attack--the deadliest attack on American soil since Japanese planes bombed Pearl Harbor during World War II. Who would devise such a scheme, and why?

Osama bin Laden, pictured here, was the son of a Saudi Arabian billionaire. He left his wealthy lifestyle behind to follow his extreme and violent beliefs.

The culprits were a terrorist group called al-Qaeda, which means "The Base" in Arabic. Al-Qaeda was created by a radical Muslim named Osama bin Laden in the late 1980s. The group fights for several goals: the destruction of Israel, a stricter interpretation of Islam, and eventually the creation of a worldwide Islamic state. In al-Qaeda's ideal world, all national boundaries will disappear, Islamic law ("sharia") will be the final authority everywhere, and Muslim clerics will rule the world.

Osama bin Laden and other members of al-Qaeda hoped the 9/11 attacks would punish the United States for its support of Israel and create a war between the nonreligious Western world (symbolized by American power) and followers of bin Laden's radical version of Islam.

Use the following activity to review some key terms related to the people behind the 9/11 attacks. Match each term with its definition on the right.