This is the country we usually call North Korea.
Our main military involvement with North Korea has, of course, been the Korean War. This bitter war, though deserving of a lot more attention than it usually gets, is very well known and very well documented in other books, and with a vast subject like All the Countries We’ve Ever Invaded, I’m sorry to say that space is limited so I can’t go into much detail here.
Basically, after the Second World War, Korea, freed from Japanese occupation, ended up divided along the 38th Parallel between a Soviet-backed regime in the north and an American-backed regime in the south. After increasing border tensions, North Korea invaded South Korea on 25 June 1950. The United Nations called for forces to resist the North Korean advance, but the North Koreans pushed deep into South Korea. However, the North Koreans were prevented from taking the key strategic port of Pusan and in September 1950 General MacArthur landed two divisions at Inchon in the North Korean rear, forcing the North Koreans to retreat rapidly as our side pursued them deep into their territory. At this point the Chinese came into the war and it was the UN forces’ turn to retreat, eventually to a line well south of Seoul. Gradually, UN forces pushed the enemy back again until the fighting ground to a halt in something of a stalemate in the area of the 38th Parallel.
British forces fought bravely in many locations during the Korean War, including the stage where UN forces pushed deep inside North Korea.