Who was the mastermind in September 11 attacks?

Khalid Sheikh Mohammed (KSM), a Pakistani, was the chief architect and mastermind behind the September 11 terrorist attacks. The chief financier of the attacks was Osama bin Laden, a Saudi.

KSM was captured by the Pakistani intelligence service in 2003, and is awaiting trial for the September 11 terror attacks, as well as other terror attacks and plots.