It is rare for both capitals of the center of conflict to be conquered. It is unusual for even one to be conquered and for the conflict to continue. But in this case, not only were both capitals conquered, and then both liberated, but one was even conquered and then liberated again in perhaps the greatest see-saw campaign of all time.
The end of World War II saw Korea artificially divided into two pieces at the 38th parallel. It might not have happened had Japan fallen to American aerial bombardments, sea-mines and island hopping campaign. It should have: the Americans were obliterating Japanese cities and cutting off its lifeline by sinking its merchant fleet. The Japanese were probably hanging by a thread, but they weren’t showing signs of caving. The Soviets finally attacked the Japanese in China, and did so in very large numbers, using veteran divisions pulled from Europe, confident with the knowledge that they were the vanquishers of Hitler’s Wehrmacht and thus easily the mightiest land force in the world. The Japanese on the Asian mainland crumbled quickly, and the Soviets advanced through northern China and into northern Korea. On August 6, 1945, the B-29 bomber Enola Gay dropped a single atomic bomb and practically obliterated the city of Hiroshima. Three days later the city of Nagasaki received an atomic bomb. Between the Soviet invasion and the two atomic bombs, the war ended quickly with the Japanese seeking surrender on August 15, 1945. The war ended on September 2, 1945, and with it was the decision of the Soviets and the Americans to cleave the centuries old unified land of Korea into two halves: North and South.
This rapidly negotiated nonchalant demarcation was to have, as have had so many other artificial divisions, long-term consequences. To the north was Communist run North Korea and on the other side of the 38th parallel was American occupied and protected, dictatorially democratic South Korea. But this division was completely artificial since the people on both sides of this border spoke the same language, had the same culture, ate the same food and were unified in every other aspect.
From the end of World War II on, both sides of the Korean Peninsula were continuously thinking about a reunited Korea, but it was the North that acted first. The United States, reacting on the assumption that this was part of a coordinated plan under Soviet oversight of the ultimate objective of world domination under Communism, felt that the attack had to be contained at all costs, even if there was little with which to contain the attack: post-war America was demobilized in spirit and body and its people were rightfully celebrating a return to normalcy.
It was 25 short air miles from the North Korean border to Seoul, the capital of South Korea. The North Koreans had amassed seven infantry divisions and an armor brigade populated with Soviet T-34/85 tanks equipped with hard hitting 85mm guns. All seven divisions and the armored brigade were made of three regiments each. Thus the invading forces totaled 24 regiments. There was also a mechanized infantry brigade. All things considered, it was actually a pretty small force to kick off what would turn into a major war. In comparison, the German invasion of Poland was launched with about 60 divisions.