In 1961 Kennedy became president and carried on Eisenhower’s scheme to invade Cuba. In April 1961, 1900 Cubans who had been supporters of Batista came ashore at the Bay of Pigs supported by "Douglas Invader" bombers. Castro’s jets shot these down and after three days the invasion force surrendered.
After this Castro sought aid from Russia, who sent ships, and Kennedy ordered constant air surveillance of Cuba, revealing that "intermediate range Ballistic Missiles" (I.R.B.M.s) had been installed in Cuba. If nuclear war-heads were present, every city within 2,500 miles was in danger. On 22nd October a quarantine or "blockade" was imposed on Cuba.