MIHOP is an acronym for "Made It Happen On Purpose", specifically in regards to the 9/11/2001 attacks on the World Trade Center and Pentagon. It alleges that the U.S. parts of the government was the initiator of the 9/11 attacks. In short, it was an inside job. The milder theory, which holds that the U.S. government merely didn't do anything to prevent a known future attack is known as LIHOP (or "Let It Happen On Purpose").