Australia was the second nation, behind the United States, to commit personnel from all three armed services to the war to defend the Republic of Korea. On June 28, 1950, Australia committed Royal Australian Navy (RAN) and Royal Australian Air Force (RAAF) elements (at that time based in Japan) to the Korean War effort. On July 1, 1950, the destroyer HMAS Bataan and frigate HMAS Shoalhaven left Japanese waters escorting U.S. troop ships to Busan. The following day, July 2, the RAAF’s 77th Squadron flew the first ground support operations over Korea, becoming the first British Commonwealth and United Nations unit to see action in the Korean War. Over the next few weeks, 77 Squadron flew numerous sorties and along with other allied air units.
In mid-July the Commander of United Nations forces in Korea requested the deployment of the Australian Army’s 3rd Battalion, The Royal Australian Regiment (3RAR) to the peninsula from Japan where it was serving. 3RAR arrived in Busan on September 28, 1950, and was incorporated into the British-led 27th Commonwealth Brigade. Alongside their Commonwealth partners, 3RAR participated throughout the Korean War and took part in action including the Battle of Gapyeong in April 1951. 3RAR was eventually joined by both the 1st and 2nd Battalions, RAR.
The RAN sent 13 ships in total, including the aircraft carrier HMAS Sydney. The RAAF contributed an air transport squadron and other elements.
Australia would ultimately be the fifth-largest contributor to the United Nations Command. Over 17,000 Australians served during the Korean War. Three-hundred and forty were killed and over 1,216 were wounded. Twenty-nine had become prisoners of war and 43 personnel remain missing in action. Australian forces remained in Korea as part of the multi-national peacekeeping force until 1957. 
Australia continues to contribute personnel in support of the UNC mission in Korea. Australia also regularly provides additional staff for training and operations. Vice Admiral Stuart Mayer is the first Australian to hold the position of UNC Deputy Commander, and only the second non-American to hold this position. Australia also fills the position of Commander UNC-Rear in Yokota, Japan.