UNC was established on 7 July 1950 following the UN's recognition of North Korean aggression against South Korea. UN member states were called to provide assistance in repelling the North's invasion, with UNC providing a cohesive command structure under which the disparate forces would operate. During the course of the war, 22 nations contributed military or medical personnel to UN Command; although the United States led the UNC and provided the bulk of its troops and funding, all participants formally fought under the auspices of the UN, with the operation classified as a "UN-led police action".