Who Is Khalid Sheikh Mohammed, Pakistani Terrorist Behind 9/11 Attacks

Regarded as one of Al-Qaeda chief Osama bin Laden's most trusted and intelligent lieutenants, Mohammed, also known as "KSM," was captured in Pakistan in March 2003.

Khalid Sheikh Mohammed, the mastermind of the September 11, 2001 hijackings -- the deadliest ever attacks on US soil -- has dedicated his life to plotting against the West.

Regarded as one of Al-Qaeda chief Osama bin Laden's most trusted and intelligent lieutenants, Mohammed, also known as "KSM," was captured in Pakistan in March 2003.

He then spent three years in secret CIA prisons before arriving in 2006 at the US navy base in Guantanamo Bay, Cuba.