The United Nations (UN) offensive in September 1950 had succeeded in pushing the North Korean army out of South Korea. By mid-November, the conflict appeared to be over, and the Canadian government only sent the 2nd Battalion of the Princess Patricia's Canadian Light Infantry (2 PPCLI) to Korea rather than an entire brigade.
On 26 November, 300,000 Chinese troops entered the conflict and pushed the UN forces back. When the PPCLI arrived in South Korea on 18 December 1950, the UN forces were hard pressed to halt the Chinese offensive. Consequently, the Canadian government dispatched the rest of the 25th Canadian Infantry Brigade Group, but it did not arrive in Korea until 4 May 1951.
The PPCLI joined the 27th British Commonwealth Brigade Group on 15 February 1951. By the end of March, the Chinese forces had advanced into South Korea, and UN forces were retreating to establish new defensive positions to the south. After the front had been stabilized, the Chinese army renewed its offensive on 22 April 1951. The 2nd Battalion of the PPCLI took up positions on Hill 667, north of the town of Kap'yong, on 23 April. The 3rd Battalion of the Royal Australian Regiment (RAR) deployed on Hill 504 to the east of Hill 677.
On 24 April, the Chinese launched a massive assault on these two hills. The RAR suffered heavy casualties but continued to fight until it received orders to withdraw. The PPCLI continued to engage the Chinese force and covered the Australian withdrawal. To the south, UN forces were feverishly preparing new defensive positions. Four companies of the PPCLI were all that stood between them and the Chinese army.
On the night of 24-25 April, the Chinese attacked Hill 677 in waves. Chinese troops employed machine guns and grenades at point-blank range, but the companies of the PPCLI repulsed every assault. The Chinese attacks continued through the night, threatening to overwhelm the Canadians. In the pre-dawn darkness, the commander of "D" company, Captain J.G.W. Mills, made a daring decision. He ordered his troops to take cover in their trenches and then radioed for an artillery barrage on his position.
As the artillery shells rained down, torrents of hot metal fragments decimated the Chinese ranks. As the sun rose, the PPCLI, although cut off from the rest of the UN forces, still held Hill 677. That morning, American transport planes dropped food, ammunition, and water to the exhausted Canadian companies.
The American president, Harry S. Truman, presented the Princess Patricia's Canadian Light Infantry a Presidential Unit Citation for its heroic defence of Hill 677. It is the only Canadian regiment to have received this honour. Truman also awarded the RAR with a Presidential Unit Citation. The 3rd Battalion Royal Australian Regiment also received the Presidential Unit Citation at Kap'yong. Britain's 1st Battalion Gloucestershire Regiment received this award for its service at the Imjin River. All three citations were given for actions that occurred within a day or so of each other during the same Chinese general offensive.