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.

The American Anti-Imperialist League was established in the United States on June 15th 1898 to battle the American annexation of the Philippines officially called is solar areas following the Spanish-American War the Anti-Imperialist League oppose annexation on economic legal and moral grounds