Two Gloucestershire Regiment veterans paid tribute to their fallen comrades during a low-key ceremony at the Gloster Valley Battle Monument.
The ferocious battle, in which soldiers held off thousands of Chinese troops for three days, was fought on top of nearby Gloster Hill in April 1951.
It remains the bloodiest battle fought by British Forces since World War II.
Pte Sam Mercer read the roll of honour of every soldier of the Gloucestershire Regiment who died either in battle or later in the prisoner of war camps.
"This was the most important moment of the visit to me," said Mr Mercer, who lost an eye and a leg in the fighting.
"One of the things I look back on with regret is that we had to leave the bodies of our fallen comrades behind to the fate of the Chinese."
Another 'Glorious Gloster', L/Cpl Harry Hawksworth said: "As young men we were just following orders, but as we get older it just gets really emotional."
The official remembrance ceremony takes place at the Gloster Valley Memorial at Solma-ri on Saturday and will involve scores of veterans from countries such as the UK, Canada, New Zealand and Australia.
A group of war veterans have returned to South Korea 60 years after fighting in the famous Battle of Imjin River.