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Military

His Majesty's Armed Forces consist of three professional service branches: the Royal Navy and Royal Marines (forming the Naval Service), the British Army and the Royal Air Force. The armed forces of the United Kingdom are managed by the Ministry of Defence and controlled by the Defence Council, chaired by the Secretary of State for Defence. The Commander-in-Chief is the British monarch, to whom members of the forces swear an oath of allegiance. The Armed Forces are charged with protecting the UK and its overseas territories, promoting the UK's global security interests and supporting international peacekeeping efforts. They are active and regular participants in NATO, including the Allied Rapid Reaction Corps, the Five Power Defence Arrangements, RIMPAC and other worldwide coalition operations. Overseas garrisons and facilities are maintained in Ascension Island, Bahrain, Belize, Brunei, Canada, Cyprus, Diego Garcia, the Falkland Islands, Germany, Gibraltar, Kenya, Oman, Qatar and Singapore.

The UK is the 34th most peaceful country in the world, according to the 2024 Global Peace Index.

According to sources which include the Stockholm International Peace Research Institute and the International Institute for Strategic Studies, the UK has either the fourth- or the fifth-highest military expenditure. Total defence spending in 2024 is estimated at 2.3% of GDP. Following the end of the Cold War, defence policy has a stated assumption that "the most demanding operations" will be undertaken as part of a coalition.