Here's What You Need to Remember: North Korea’s arsenal isn’t anywhere nearly as advanced as that of the United States, but it is massive. Some analysts have suggested that the regime’s huge stockpile of traditional artillery and rockets would “flatten Seoul in the first half-hour of any confrontation.”

It’s difficult to try to keep up with developments in the latest round of saber rattling between the United States and North Korea. U.S. President Donald Trump and Korean “supreme leader” Kim Jong-un have repeatedly traded verbal barbs via Twitter and more formal avenues amid news of naval redeployments, massive live-fire artillery exercises, United Nations condemnations and rumors of troop movements by regional powers.

The United States would have an obvious and distinct advantage over North Korea in a direct military engagement. That doesn’t mean that a war wouldn’t be a grueling and costly endeavor. North Korea’s military is dilapidated and antiquated, but it’s still one of the largest militaries in the world. When the two countries clashed before, from 1950 to 1953, the conflict ended in a virtual draw along the 38th parallel.

Of course, the hundreds of thousands of soldiers China sent to save its North Korean ally played a decisive role in that outcome, but the Korean People’s Army itself put up a formidable fight against the much more powerful United States and its allies. The KPA inflicted considerable casualties in a blitzkrieg-like assault through the south and quickly seized huge swaths of territory, compelling the United States to implement a scorched-earth policy that inflicted a tremendous death toll.

On a per-capita basis, the Korean War was one of the deadliest wars in modern history, especially for the civilian population of North Korea. The scale of the devastation shocked and disgusted the American military personnel who witnessed it, including some who had fought in the most horrific battles of World War II.

World War II was by far the bloodiest war in history. Estimates of the death toll range from 60 million to more than 85 million, with some suggesting that the number is actually even higher and that 50 million civilians may have perished in China alone. Even the lower estimates would account for roughly three percent of the world’s estimated population of 2.3 billion in 1940.

These are staggering numbers, and the death rate during the Korean War was comparable to what occurred in the hardest hit countries of World War II.

Several factors contributed to the high casualty ratios. The Korean Peninsula is densely populated. Rapidly shifting front lines often left civilians trapped in combat zones. Both sides committed numerous massacres and carried out mass executions of political prisoners. Modern aircraft carried out a vast bombing campaign, dropping massive loads of napalm along with standard bombs.

In fact, by the end of the war, the United States and its allies had dropped more bombs on the Korean Peninsula, the overwhelming majority of them on North Korea, than they had in the entire Pacific Theater of World War II.

“The physical destruction and loss of life on both sides was almost beyond comprehension, but the North suffered the greater damage, due to American saturation bombing and the scorched-earth policy of the retreating U.N. forces,” historian Charles K. Armstrong wrote in an essay for the Asia-Pacific Journal.

“The U.S. Air Force estimated that North Korea’s destruction was proportionately greater than that of Japan in the Second World War, where the U.S. had turned 64 major cities to rubble and used the atomic bomb to destroy two others. American planes dropped 635,000 tons of bombs on Korea—that is, essentially on North Korea—including 32,557 tons of napalm, compared to 503,000 tons of bombs dropped in the entire Pacific theatre of World War II.”

As Armstrong explains, this resulted in almost unparalleled devastation.

“The number of Korean dead, injured or missing by war’s end approached three million, ten percent of the overall population. The majority of those killed were in the North, which had half of the population of the South; although the DPRK does not have official figures, possibly twelve to fifteen percent of the population was killed in the war, a figure close to or surpassing the proportion of Soviet citizens killed in World War II.”

U.S. officers and soldiers who surveyed the results of the air campaign in Korea were both awestruck and revolted. In his controversial book Soldier, Lt. Col. Anthony Herbert collects reflections on the carnage from America’s most prominent generals of the day.

“We burned down just about every city in North Korea and South Korea both,” recalled Gen. Curtis LeMay. “We killed off over a million civilian Koreans and drove several million more from their homes, with the inevitable additional tragedies bound to ensue.”

LeMay was no newcomer to the horrors of war. He led several B-17 Flying Fortress bombing raids deep into German territory before going on to command the strategic bombing campaign against Japan, including the firebombings of Tokyo.

Another decorated veteran of World War II, Air Force four-star Gen. Emmett E. “Rosie” O’Donnell, Jr., who later served as Commander in Chief of Pacific Air Forces from 1959 to 1963, collaborated LeMay’s and Armstrong’s assessments.

“I would say that the entire, almost the entire Korean Peninsula is a terrible mess. Everything is destroyed,” O’Donnell said. “There is nothing left standing worthy of the name.”

Perhaps the most scathing account of the destruction came from Gen. Douglas MacArthur.

MacArthur had become a national hero for his exploits as commander of the U.S. Army Forces in the Far East during the Philippines campaign of World War II, and as Supreme Commander for the Allied Powers during the occupation of Japan before he was named Commander-in-Chief of the United Nations Command at the onset of the Korean Conflict.

Despite his long and storied career as an officer, he began butting heads with Pres. Harry Truman over how the war in Korea was being conducted. This led to Truman relieving him of his command on April 11, 1951. MacArthur subsequently testified at joint hearings before the Senate’s Committee on Armed Services and Committee on Foreign Relations to discuss his dismissal and the “Military Situation in the Far East.”

“I shrink—I shrink with a horror that I cannot express in words—at this continuous slaughter of men in Korea,” MacArthur lamented during the hearings.

“The war in Korea has already almost destroyed that nation of 20,000,000 people. I have never seen such devastation. I have seen, I guess, as much blood and disaster as any living man, and it just curdled my stomach the last time I was there. After I looked at the wreckage and those thousands of women and children and everything, I vomited … If you go on indefinitely, you are perpetuating a slaughter such as I have never heard of in the history of mankind.”

Neither North Korea nor the United States has ever been able to truly come to terms with the havoc wrought during the conflict.

In North Korea, the war is often referred to as the Victorious Fatherland Liberation War, with the Korean People’s Army being cast as the valiant protector of the virtuous Korean people in the face of American imperialism. North Korean casualties and atrocities—as well as the U.S. strategic bombing campaign—are downplayed or ignored while victories are often exaggerated. This revisionist history falls in line with the “Great Leader” cult of personality promulgated by Kim Il-sung and his heirs who have led the country since the end of the war.

In the United States, the war is somewhat lost in the shadows of World War II and the Vietnam War. It came as Americans were still recovering from the former and was, by comparison, a much smaller and shorter conflict. It lacked the media coverage and cultural impact of the prolonged war in Vietnam. Its legacy was also marred by a preponderance of atrocities—some of them carried out by the United States and its allies—and what in the minds of many Americans ultimately amounted to a defeat by a smaller and weaker enemy.

It wasn’t until 1999 that the United States acknowledged—after a lengthy investigation by the Associated Press—that a 1950 letter from U.S. Ambassador John J. Muccio authorized commanders in the field to adopt a policy of openly massacring civilians.

The policy led to massacres in No Gun Ri and Pohang, among others, in which U.S. soldiers and seamen knowingly fired on civilians. Refugees fleeing North Korea were particularly susceptible to attacks from the U.S. and South Korean militaries under the pretense that North Korean soldiers had infiltrated their numbers in order to orchestrate sneak strikes. Hundreds at a time were killed, many of them women and children.

”We just annihilated them,” Norman Tinkler, a former machine gunner, later told the Associated Press of the massacre at No Gun Ri.

Edward L. Daily, another soldier present at the No Gun Ri, was still haunted by what he witnessed there decades later.