https://en.wikipedia.org/wiki/Bombing_of_North_Korea

During the campaign, conventional weapons such as explosives, incendiary bombs, and napalm destroyed nearly all of the country's cities and towns, including an estimated 85% of its buildings.

A total of 635,000 tons of bombs, including 32,557 tons of napalm, were dropped on Korea. By comparison, the U.S. dropped 1.6 million tons in the European theater and 500,000 tons in the Pacific theater during all of World War II (including 160,000 on Japan). North Korea ranks alongside Cambodia (500,000 tons), Laos (2 million tons), and South Vietnam (4 million tons) as among the most heavily-bombed countries in history.

In an interview with U.S. Air Force historians in 1988, USAF General Curtis LeMay, who was also head of the U.S. Strategic Air Command, commented on efforts to win the war as a whole, including the strategic bombing campaign, saying “Right at the start of the war, unofficially, I slipped a message in "under the carpet" in the Pentagon that we ought to turn SAC lose with some incendiaries on some North Korean towns. The answer came back, under the carpet again, that there would be too many civilian casualties; we couldn't do anything like that. We went over there and fought the war and eventually burned down every town in North Korea anyway, some way or another, and some in South Korea, too......Over a period of three years or so we killed off, what, 20 percent of the population of Korea, as direct casualties of war or from starvation and exposure? Over a period of three years, this seemed to be acceptable to everybody, but to kill a few people at the start right away, no, we can't seem to stomach that.”

Sahr-Conway Lanz, who holds a Ph.D. in the history of American foreign relations, has written extensively about the legacy and impact on American discourse on the international norm of noncombatant immunity. He states:

"During the war, American military and civilian officials stretched the term "military target" to include virtually all human-made structures, capitalizing on the vague distinction between the military and civilian segments of an enemy society. They came to apply the logic of total war to the destruction of the civil infrastructure in North Korea. Because almost any building could serve a military purpose, even if a minor one, nearly the entire physical infrastructure behind enemy lines was deemed a military target and open to attack. This expansive definition, along with the optimism about sparing civilians that is reinforced, worked to obscure in American awareness the suffering of Korean civilians in which U.S. firebombing was contributing."

The song was inspired by Korean war veteran that John McCrea met in a bar.

https://www.youtube.com/watch?v=52Rgsihd6WM