Hey there! I'm happy to help you out!
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THE WARSAW PACT
If you didn't know already, Warsaw is the capital city of Poland. :)
The Warsaw Pact was basically a big friendship/defense treaty that was signed by a lot of the Eastern European countries. It was made in 1955 and it was basically a big alliance made between Poland, East Germany, The Soviet Union, Czechoslovakia, Hungary, Bulgaria, Albania, and Romania. It basically was so that a lot of these countries could turn communist as well.
This is was basically NATO's counterpart/archenemy. The countries in NATO were countries such as the U.S., UK, France, Greece, Spain, Italy, etc. These guys were opposed to many of the things the Warsaw Pact countries were doing.
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THE KOREAN WAR
During the Cold War, one of the U.S.'s main goals was to stop the spread of communism. One very communist country during the time was North Korea. South Korea was not communist. In the summer of 1950, North Korea invaded South Korea, so the U.S. jumped in to try to stop them, and that basically caused the Korean War.
The exact line that the North Koreans crossed is known as the the 38th parallel because it's 38 degrees north from the equator, and this line of latitude split the two countries.
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I hope that this helps! Have a wonderful day!