In late April 1951 a massive Chinese attack (concentrated against 29 Brigade) fell on the UN line. In three days of savage fighting the 1st Battalion of the Gloucestershire Regiment was cut off and destroyed, while the remaining 29 Brigade fought off massed Chinese attacks. By 25 April the remaining three battalions of 29 Brigade, along with the supporting arms, had been forced to withdraw. On 26 April 29 Brigade was relieved by American units and refitted. 27 Commonwealth Brigade was also heavily attacked further east, and although no units were cut off and destroyed, they too were forced to give ground after massed Chinese attacks. During the later stages the relief of 27 Commonwealth Brigade with the newly formed 28 Commonwealth Brigade took place as UN forces retreated to a new defensive position covering Seoul.
Back in Britain, the increase in defence spending due to the United Kingdom's involvement in Korea caused a split in the Labour government. At the resulting general election in November 1951 the Conservatives took power under Winston Churchill.
The Chinese offensive tailed off in May 1953 and the front settled into a line that would remain essentially unchanged until the armistice was signed on 27 July 1953. Reinforcements from UN countries still headed for Korea and the 1st Commonwealth Division was formed at the end of July 1951 - comprising the 28 Commonwealth Brigade, 29 Brigade and 25 Canadian Brigade. The British and Commonwealth naval forces were formed into the West Korean Support Group while the United States Navy formed the East Korean Support Group.
Over the course of the three years of fighting the Royal Navy contributed an array of aircraft carriers, cruisers, destroyers and support vessels. Australian, New Zealand and Canadian destroyers and frigates serving with the West Korean Support Group represented Commonwealth navies and Australia also sent an aircraft carrier. The Fleet Air Arm provided Britain's air contribution with piston engine planes and newer jets, operating against ground targets and carrying out air superiority tasks. Support was also provided by the guns of the cruisers, destroyers and frigates firing at North Korean and Chinese positions on the coast.
As both sides were unwilling to escalate the fighting, the conflict descended into stalemate. After months of talks to overcome mistrust and suspicion on both sides, an armistice was signed on 27 July 1953. But it was an armistice, not an end to war. The armistice and the demilitarised zone dividing North and South Korea still hold today and South Korean and American forces man the fortifications.