1945 - USA drops atomic bombs (A bombs) on Hiroshima and Nagasaki.
1949 - USSR develops first A bomb which ends USA's monopoly.
1952 - USA's first Hydrogen bomb (H bomb), X2500 times more powerful
1953 - USSR tests its own H bomb
1957 - Sputnik 1 launched by USSR - the first ICBM
1959 - USA's Polaris subs