Since the GAF was formed in 1985, it has been active in UN and African Union peacekeeping missions. It has been classed as a Tier 2 peacekeeping contributor and was described by the Center on International Cooperation as a regional leader in peacekeeping. It dispatched soldiers to Liberia as part of ECOMOG from 1990 to 1991, during which two Gambian soldiers were killed. It has since contributed troops to ECOMIL, UNMIL, and UNAMID. Responsibility for the military has rested directly with the President since Jammeh seized power at the head of a bloodless military coup in 1994. Jammeh also created the role of Chief of the Defence Staff, who is the senior military officer responsible for the day-to-day operations of the Gambia Armed Forces. Between 1958 and 1985, the Gambia did not have a military, but the Gambia Field Force existed as a paramilitary wing of the police. The military tradition of the Gambia can be traced to the Gambia Regiment of the British Army, that existed from 1901 to 1958 and fought in World War I and World War II. In 2017, Gambia signed the UN treaty on the Prohibition of Nuclear Weapons.