On June 25, 1950, the North Korean Army began the invasion of South Korea (Republic of Korea), crossing the 38th parallel. When the United Nations Security Council required military aid from the international community to protect the Republic of Korea, Australia responded by sending two units: the Australian Army’s 3rd Battalion, Royal Australian Regiment (3 RAR), and the No 77 Squadron Royal Australian Air Force (RAAF), which was armed with P-51 Mustang fighters and used in the ground attack and anti-tank role.
Composed of 1,200 infantry men, the 3rd Battalion was part of the 27th Commonwealth Brigade; under the command of Lt Cnl Charles Green, they fought fiercely and successfully in the Battle of Kapyong, from April 22 to April 25, 1951, in which they took strategic North Korean defensive positions. The men of the Australian 3rd Battalion also got engaged in the Battle of Yongju, which was the first major military engagement of the war they got involved in (October 21, 1950), in Operation Killer (February-March 1951), Operation Ripper (March-April 1951), the Battle of Maryang San (October 1951), and other military encounters. For their gallantry and effectiveness, the 3rd Battalion, Royal Australian Regiment, obtained the US Presidential Unit Citation.