It is widely known that the Nazis, in Operation Himmler, faked attacks on their own people and resources which they blamed on the Poles, to justify the invasion of Poland.
And it has now been persuasively argued -- as shown, for example, in this History Channel video -- that Nazis set fire to their own government building and blamed that fire on others (if you have trouble playing the clip, it is because the website hosting the clip requires you to download the clip before playing it). The fire was the event which justified Hitler's seizure of power and suspension of liberties.
And in the early 1950s, agents of an Israeli terrorist cell operating in Egypt planted bombs in several buildings, including U.S. diplomatic facilities, then left behind "evidence" implicating the Arabs as the culprits (one of the bombs detonated prematurely, allowing the Egyptians to identify the bombers). Israel's Defense Minister was brought down by the scandal, along with the entire Israeli government. See also this confirmation.
And the Russian KGB apparently conducted a wave of bombings in Russia in order to justify war against Chechnya and put Vladimir Putin into power.
The Turkish government has carried out bombings and blamed it on the PKK in order to justify a crackdown on that group.
This is called "false flag terrorism", where a government attacks its own people then blames others in order to justify its goals
But NOT the U.S.
It is logical to assume that, even if other countries have carried out false flag operations (especially horrible regimes such as, say, the Nazis), the U.S. has never done so.
Well, as shown by this BBC special (which contains interviews with some of the key players), it is probable that America knew of the Japanese plan to attack Pearl Harbor -- down to the exact date of the attack -- and allowed it to happen to justify America's entry into World War II. See also this short essay by a highly-praised historian summarizing some of the key points (the historian, a World War II veteran, actually agreed with this strategy for getting America into the war, and so does not have any axe to grind). The Pearl Harbor conspiracy involved hundreds of military personnel. Moreover, the White House apparently had, a year earlier, launched an 8-point plan to provoke Japan into war against the U.S. (including, for example, an oil embargo). And -- most stunning -- the FDR administration took numerous affirmative steps to ensure that the Japanese attack would be successful.
And, as confirmed by a former Italian Prime Minister, an Italian judge, and the former head of Italian counterintelligence, NATO, with the help of U.S. and foreign special forces, carried out terror bombings in Italy and blamed the communists, in order to rally people’s support for their governments in Europe in their fight against communism. As one participant in this formerly-secret program stated: "You had to attack civilians, people, women, children, innocent people, unknown people far removed from any political game. The reason was quite simple. They were supposed to force these people, the Italian public, to turn to the state to ask for greater security."
Moreover, recently declassified documents show that in the 1960's, the American Joint Chiefs of Staff signed off on a plan to blow up AMERICAN airplanes (using an elaborate plan involving the switching of airplanes), and also to commit terrorist acts on American soil, and then to blame it on the Cubans in order to justify an invasion of Cuba. If you view no other links in this article, please read the following ABC news report; the official documents; and watch this interview with the former Washington Investigative Producer for ABC's World News Tonight with Peter Jennings.
Therefore, before you dismiss as a tinfoil hat conspiracy claims about 9/11, please take a look at the historical record.
Postscript: the examples discussed above are only a small handful of the many potential examples of false flag operations. Just two more examples:
Australia's largest newspaper quoted the well-respected former Indonesian president as saying that the government had a role in the Bali bombings (apparently, Muslim governments play this game as well)
And according to the London Times, "The man accused of supplying the dynamite used in the al-Qaeda train bombings in Madrid was in possession of the private telephone number of the head of Spain's Civil Guard bomb squad . . . . The revelation has raised fresh concerns in Madrid about links between those held responsible for the March bombings, which killed 190 people, and Spain’s security services". See also this article showing that two of the bombers appear to be government informants.