When governments or organizations (usually connected to the former) stage highly sophisticated attacks on their own or foreign soil with the purpose of placing the blame on a desirable enemy foreign or domestic, one who has otherwise done no wrong. Essentially a setup, it provides the government entity with an excuse via fabricated evidence in complicity with media to fulfill its various agendas (i.e. war or law making).
As false flag operations gain further ground and frequency, the better you know their history, the sooner you can recognize when they are about to happen or as they occur.
As practically the only anti-war candidate, Ron Paul recently pointed out such a fact to the other puppet candidates during a debate. The other candidates are heartily calling for World War III which could possibly destroy the planet by dressing up an Iranian invasion, whereas Paul points out that the Iraq war (which has massacred over one million Iraqis) was based on an utter and complete fabricated lie.