One guy is all it takes. Below is from testimony Hermann Goering gave at the Nuremburg trials. Yes, he was among the worst of the worst of the Nazis...but what he says below is 100% accurate:

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Goering: Why, of course, the people don't want war. Why would some poor slob on a farm want to risk his life in a war when the best that he can get out of it is to come back to his farm in one piece? Naturally, the common people don't want war; neither in Russia nor in England nor in America, nor for that matter in Germany. That is understood. But, after all, it is the leaders of the country who determine the policy and it is always a simple matter to drag the people along, whether it is a democracy or a fascist dictatorship or a Parliament or a Communist dictatorship.

Gilbert: There is one difference. In a democracy, the people have some say in the matter through their elected representatives, and in the United States only Congress can declare wars.

Göring: Oh, that is all well and good, but, voice or no voice, the people can always be brought to the bidding of the leaders. That is easy. All you have to do is tell them they are being attacked and denounce the pacifists for lack of patriotism and exposing the country to danger. It works the same way in any country.

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Reread that last sentence, and then think back to how America was lied - lied! - into invading Iraq. They were not working on nuclear weapons to attack America...but anyone who said otherwise was denounced, as Goering put it, for "for lack of patriotism and exposing the country to danger".

One guy really is all it takes. That's how it's been throughout nearly all of human history.