Today, Russian nuclear forces are probably at the U.S. equivalent of DEFCON 3 or DEFCON 2, which is very rare in history, occurring only during such major events as the 1956 Suez Crisis, 1958 Berlin Crisis, 1962 Cuban Missile Crisis, 1968 invasion of Czechoslovakia, 1973 Yom Kippur War, 1983 Able Archer NATO nuclear exercise, and 1991 Soviet coup attempt against Premier Gorbachev, for example. Today, U.S. nuclear forces are not mobilized, are at their normal everyday state of readiness: DEFCON 5.