Able Archer 83 was a ten-day NATO command post exercise starting on November 2, 1983 that spanned Western Europe, centred on SHAPE's Headquarters situated at Casteau, north of the Belgian city of Mons. Able Archer exercises simulated a period of conflict escalation, culminating in a coordinated nuclear release. The 1983 exercise incorporated a new, unique format of coded communication, radio silences, participation by heads of state, and a simulated DEFCON 1 nuclear alert.
The realistic nature of the 1983 exercise, coupled with deteriorating relations between the United States and the Soviet Union and the anticipated arrival of Pershing II nuclear missiles in Europe, led some in the USSR to believe that Able Archer 83 was a ruse of war, obscuring preparations for a genuine nuclear first strike. This relatively obscure incident is considered by many historians to be the closest the world has come to nuclear war since the Cuban Missile Crisis of 1962 The threat of nuclear war abruptly ended with the conclusion of the Able Archer 83 exercise on November 11.
The armed forces of the United Kingdom, commonly known as the British Armed Forces or His/Her Majesty's Armed Forces, and sometimes legally the Armed Forces of the Crown, encompasses a navy, an army, and an air force. With a reported personnel strength of 425,500 in 2006 (191,900 regular force, 191,300 regular reserve, and 42,300 volunteer reserve), the British Armed Forces constitutes one of the largest militaries in Europe, though only the 26th largest in the world by number of troops. The British Armed Forces however have the third highest declared expenditure of any military in the world. Their Commander-in-Chief is the British monarch, HM Queen Elizabeth II and they are managed by the Defence Council of the Ministry of Defence. Consistent with longstanding constitutional convention, however, the Prime Minister holds de facto authority over the armed forces.
The British Armed Forces are charged with protecting the United Kingdom and its overseas territories, promoting Britain's wider security interests, and supporting international peacekeeping efforts. They are active and regular participants in NATO and other coalition operations.