Major lessons learned from world war 2?

The war provided two contradictory lessons: the first was that war was to be avoided at all costs, the second was that democracies had to be ready to resist aggression. The second lesson led most western European states, including Germany, to rearm and join the Atlantic alliance.

One other lesson includes that countries have to be careful of how they handle diplomatic relations with other countries.

Explanation:

History.

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