The document discusses the nuclear arms race between the US and USSR from 1945 to 1960. Both countries rapidly developed more powerful nuclear weapons and delivery systems out of mutual distrust and a desire to gain a strategic advantage. This included the US and USSR each developing intercontinental ballistic missiles, nuclear submarines, and bombers capable of carrying nuclear payloads. Attempts at arms control negotiations failed due to a lack of trust and open inspections. Growing tensions came to a head in 1960 when an American U-2 spy plane was shot down over the Soviet Union, causing the Paris Summit between Eisenhower and Khrushchev to collapse and further hardening attitudes in the Cold War.