Following the Second World War, most countries in the Americas, including every country in Central America, Mexico, and the United States, signed the Inter-American Treaty of Reciprocal Assistance in 1947, a treaty that committed its signors to the doctrine of hemispheric defence. A similar treaty of collective defence between Canada and the United States was arranged through NATO. In April 1948, the Organization of American States was created during the Ninth International Conference of American States held in Bogotá, with member states pledging to fight communism on the American continent. The American government supported the National Liberation Party of Costa Rica during the 1948 Costa Rican Civil War, as a result of their opposition to the communist government.