The United Kingdom dispatched the second largest number of troops to Korea. The participation of the United Kingdom was done before the UN forces were established. The British Army first sent the 27th Brigade which was activated with two battalions from Hongkong and other supporting units, and upon arrival in Korea the brigade was immediately committed to the battle of the Nakdong Bulge. Later on, the 27th Brigade took part in advancing northward to the Yalu River. And later the United Kingdom dispatched one more brigade, the 29th Brigade.

The 29th Brigade suffered a lot of casualties at the battle of Seolmari near the Imjin River when China launched the 5th phase of attack. Despite these sacrifices, the 29th Brigade made a great contribution to the operations of the 8th US Army. To be more specific, on April 22, 1951, when the defense line of the ROK 1st Division broke down, the Gloucester Battalion of 29th Brigade on the right of the ROK 1st Division suffered a lot of casualties. Despite these casualties, however, the 29th Brigade held the Seolmari area for three days, so that the brigade was able to save allied units on both sides of the area.

As more troops of the British Commonwealth came in on July 28, 1951,these units were organized into the 1st Commonwealth Division. This Division was made up of the units from 6 countries: United Kingdom, Australia, Canada, New Zealand, Belgium, and Luxembourg. Such a composition was quite unique in the worlds military history.

On June 29, 1950, the UK Navy sent one aircraft carrier, two cruisers, two destroyers, and three frigates, and helped the US naval operations on the East Sea. Later, an estimated total of about 17,000 Navy soldiers of the UK participated in the Korean War, and 50 British warships took turns to carryout naval operations until the end of the war.