I remembered how each time that the democracies failed to act, it had encouraged the aggressors to keep going ahead. Communism was acting in Korea just as Hitler, Mussolini and the Japanese had acted ten, fifteen and twenty years earlier…. If this was allowed to go unchallenged it would mean a third world war, just as similar incidents had brought on a second world war.

• Truman on Korea

If I may refer again to history; we failed to halt Hirohito, Mussolini and Hitler by not acting in unity and in time. That marked the beginning of many years of stark tragedy and desperate peril. May it not be that our nations have learned something from that lesson?

• Eisenhower on Vietnam

Nor would surrender in Vietnam bring peace, because we learned from Hitler at Munich that success only feeds the appetite of aggression. The battle would be renewed …bringing with it perhaps even larger and crueler conflict, as we learned from the lessons of history.

• Johnson on Vietnam

We succeeded in the struggle for freedom in Europe because we and our allies remain stalwart. Keeping the peace in the Middle East will require no less. We're beginning a new era. This new era can be full of promise, an age of freedom, a time of peace for all peoples. But if history teaches us anything, it is that we must resist aggression or it will destroy our freedoms. Appeasement does not work. As was the case in the 1930's, we see in Saddam Hussein an aggressive dictator threatening his neighbors.

• George H. W. Bush on Kuwait

We are not deceived by their pretenses to piety. We have seen their kind before. They are the heirs of all the murderous ideologies of the 20th century. By sacrificing human life to serve their radical visions -- by abandoning every value except the will to power -- they follow in the path of fascism, and Nazism, and totalitarianism. And they will follow that path all the way, to where it ends: in history's unmarked grave of discarded lies

• George W Bush on Afghanistan

The cause of peace requires all free nations to recognize new and undeniable realities. In the 20th century, some chose to appease murderous dictators, whose threats were allowed to grow into genocide and global war. In this century, when evil men plot chemical, biological and nuclear terror, a policy of appeasement could bring destruction of a kind never before seen on this earth.

• George W Bush on Iraq