A communist dictator named Fidel Castro took over Cuba in 1959.
He allowed Soviet military forces to establish bases in Cuba. Soviet submarines, troops, ships, & jet fighters were stationed inside Cuba. The USA felt threatened by having Soviet forces so close. (Cuba is 90 miles from USA)
President Jack Kennedy ordered an invasion of Cuba. The US military trained and armed Cuban citizens to fight back and destroy the communist government. The invasion landed in the Bay of Pigs on 17 April 1961. Castro captured or killed the attackers.
Nuclear missiles launched from Cuba could hit Washington; D.C. in five minutes. This would not be enough time to evacuate. 80,000,000 Americans were within range of Soviet nuclear missiles.
JFK ordered the USAF to begin U-2 flights over Cuba. These U-2 flights took photographs indicating the buildup of Soviet forces.
JFK was staring down the barrel of nuclear gun pointed at the head of the USA. JFK did not believe in appeasement. It didn’t stop Hitler. But, fighting a nuclear WW III would kill tens of millions in the United States. Kennedy leaned heavily on his brother, RFK.