By the summer of 1951, the Korean War had reached a stalemate a few miles north of the 38th parallel where UN and Communist forces clashed in several relatively small but bloody battles.
The Battle of Bloody Ridge from mid-August to early September 1951 was an attempt by American and Republic of Korea (ROK) forces to seize a ridge a few miles north of the 38th parallel that was being used by the North Korean People’s Army (NKPA) as an observation post to call in artillery fire on a UN supply road. After a series of fierce hand-to-hand assaults and repulsions, the NKPA finally abandoned the hill. 2,700 UN and ~15,000 NKPA troops were killed or wounded with few prisoners taken by either side.
After withdrawing from Bloody Ridge, the NKPA set up new positions only ~1,500 yards away on a seven-mile-long hill that became known as Heartbreak Ridge. With intense attacks and counterattacks, the battle for Heartbreak Ridge from mid-September to mid-October 1951 proved even more difficult than that for Bloody Ridge.
With continual NKPA reinforcements and resupply, it became clear that repeated UN infantry assaults on the ridge would not succeed. A new UN plan was devised to cut the ridge off from further reinforcement. On October 11th, with >30 tanks, artillery and airplane support, the UN 2nd Division attacked the ridge just as the Chinese 204th Division was moving up to relieve the NKPA. The Chinese division suffered heavy casualties but managed to damage five Sherman tanks before the Americans halted the offensive.
On October 12, with reinforced anti-tank trenches and a battalion of anti-tank guns, Chinese forces halted a UN attack, destroying or damaging 18 tanks. Subsequent battles were extremely brutal and costly.
After 30 days of combat, American and French forces eventually secured Heartbreak Ridge. But with 38 armored vehicles destroyed and nine damaged, UN forces did not penetrate the valley to reach the town of Mundung-ni. The defense of the Mundung-ni Valley is now celebrated in North Korea as the victorious battle of Height 1211
With the loss of >3,700 American and French and an estimated 25,000 North Korean and Chinese casualties, the UN command decided that battles like Heartbreak Ridge were not worth the high cost in blood for the relatively small amount of terrain captured.