From 1961, Portugal became involved in fighting against nationalist movements in its African overseas territories, the series of conflicts becoming known as the Portuguese Colonial War. Portugal had deployed a detachment of F-86 Sabres to Portuguese Guinea in August 1961, prior to the outbreak of major fighting, but was forced to withdraw the jet fighters back to Europe owing to pressure from the United States and the United Nations, who imposed an arms embargo. This left a gap in air cover for Portugal's African colonies, both in the close air support role, and in the air defence role.