The Armed Forces in the Korean War

Over six million soldiers, sailors and airmen fought on both sides in the Korean War...

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More than three million of these were communists from North Korea, China and Russia. Opposing them were almost three million from South Korea and from 21 United Nations (UN) countries including Australia.

Not all of the six million were present at one time. The war began with only 200,000 North Koreans fighting 100,000 South Korean personnel. With the arrival of the UN, and later the Chinese armies, there were a million combatants present one year after the war began. By war's end there were more than two million ranged along the ceasefire line – 1,100,000 UN and South Koreans facing 1,200,000 North Koreans and Chinese. The Soviet Union's contribution was always small and included medical units from the Soviets' allies Hungary, Czechoslovakia, Poland, Bulgaria and Romania.

There is a constant flow of personnel in and out of armed forces. Newly trained arrivals are needed to replace losses from battle and sickness. Also personnel often serve a period in the theatre of war and then return home to rest, and are replaced by new troops. The Chinese army for instance, was never stronger than 900,000 at any one time, yet 2,200,000 Chinese served in Korea. The personnel of UN army and air units usually served for one year and were then replaced. This does not mean the unit itself always left the country. The Royal Australian Air Force's 77 Squadron served in Korea throughout the war but its members were replaced several times over in the course of the conflict. Ships of the Royal Australian Navy (RAN) served from six months to a year in Korean waters before returning to Australia. In this way nine RAN ships served there, but not more than two at a time. Of the 17,000 Australians who fought in the Korean War, there were never more than 4000 present at any moment.

The very increase in the size of the armed forces contributed to the stalemate of the last two years of the war. In the early manoeuvre phase the armies were too small to hold a strong line across the 250-kilometre wide peninsula so an enemy attack leading to a breakthrough was often possible. Later armies of more than a million on each side found the line could be strongly held all along its length, and a breakthrough became impossible or too expensive in lives.