On 14 October 1962 A US spy plane took photographs which showed Soviet missile bases being built on Cuba.
From 16 October Kennedy spent one week asking his defence chiefs for possible reactions and considering alternatives.
Troops were moved into Florida and nuclear bomber squadrons were put on full alert.
Khrushchev now sent two letters. One was defiant. The second offered a compromise. The sites would be destroyed if the USA agreed to leave Cuba alone.
Kennedy also suggested that the two leaders should begin talks on arms reduction.