What was the name of the theory that said that if one country in a region fell to Communism, others would surely follow?

domino theory

The domino theory was a theory prominent from the 1950s to the 1980s that posited that if one country in a region came under the influence of communism, then the surrounding countries would follow in a domino effect.

Explanation:

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the pogroms became known as kristallnacht, the "night of shattered glass," for the shattered glass from the store windows that littered the streets. the morning after the pogroms 30,000 german jewish men were arrested for the "crime" of being jewish and sent to concentration camps, where hundreds of them perished.