10 Facts About the Korean War

Seventy-five years after the beginning of the Korean War, we’re still no closer to a peaceful ending of the conflict. Here’s what you need to know about what’s come to be called “The Forgotten War.”

1. The CIA didn’t believe North Korea would invade South Korea.
2. The American occupying force in Japan provided troops for the Korean War.
3. The North Koreans captured an American general.
4. The Army built an impromptu special operations unit.
5. The Korean War combined old tactics and new ones on land, sea, and air.
6. The 38th parallel is a recurring theme before, during, and after the war.
7. The Korean War goes by many names.
8. The Korean War provided an early victory for an American intelligence agency.
9. The United States had dropped the Bomb only five years earlier, and was ready to do it again.
10. The Korean War never ended.

The CIA didn’t believe North Korea would invade South Korea.

Months before the North Korean Army crossed the 38th parallel, the CIA noted the southward movement of their forces, but called it a defensive measure, and called the possibility of an invasion “unlikely.” On June 24, 1950, Dean Acheson, the Secretary of State, had to telephone President Harry Truman. “Mr. President,” he said, “I have very serious news. The North Koreans have invaded South Korea.” (The start of the war is universally given as June 25, but due to time zones it was still June 24 in the United States.)

The American occupying force in Japan provided troops for the Korean War.

At the war’s start, it was pretty clear that the Republic of Korea’s forces were outmatched by the North Korean Army. General MacArthur personally went to the front lines to get a look at the situation. He quickly requested ground troops to help save the situation. President Truman eventually authorized the movement of troops from Japan to Korea. The troops, coming from the relatively peaceful job of occupying Japan following World War II, were something less than battle-ready—especially when compared with the North Korean veterans. It was during the successful six-week defense of Busan, South Korea, that American (and United Nations) forces were finally hardened for war.

The North Koreans captured an American general.

A month after the war broke out, Major General William F. Dean, commander of 24th Infantry Division, was separated from his forces in Taejon while trying to help wounded soldiers. He was out seeking water for a particularly injured G.I. when he fell down a steep hill and was knocked unconscious. He would be isolated in the mountains for the next 36 days, losing at least 60 pounds in addition to the broken shoulder and head wound he had sustained. When two South Koreans found him, they pretended to lead him to safety, but in fact brought him to a North Korean ambush site. Though Dean tried to fight his captors, but after weeks of little eating he was too weak to resist for long. He was taken prisoner on August 25, 1950, and remained prisoner until the end of the war.

The Army built an impromptu special operations unit.

The United States lacked a guerrilla warfare capability at the start of the Korean War, and had to put one together, fast. The result was the 8240th Army Unit, comprised of Rangers and other soldiers with unconventional warfare experience from World War II. They advised indigenous “partisan forces” in Korea on how to fight behind enemy lines to undermine the North Korean Army. At its height, the unit advised thousands of partisan fighters.

The Korean War combined old tactics and new ones on land, sea, and air.

The paratroopers of the 187th Airborne Regimental Combat Team (known as the “Rakkasans”) conducted many of the airborne operations of the Korean War [PDF]. They jumped into Sunch'ŏn, North Korea in 1950, and Munsan-ni, South Korea in 1951. The Rakkasans fought in a total of six campaigns in Korea. Today, the unit’s heirs are part of 101st Airborne Division (Air Assault).

The Battle of Inchon (1950) was an amphibious invasion of Incheon (as it’s romanized today) from the Yellow Sea. It was a major victory for United Nations forces, and turned around what was then a losing war. The force was commanded by General of the Army Douglas MacArthur.

Meanwhile, the Korean War was the first war fought between jet airplanes. Propeller-driven aircraft gave way to planes like F-80 Shooting Stars and Soviet MiG-15s.

The 38th parallel is a recurring theme before, during, and after the war.

In 1896, the Japanese government proposed to the Russian government that Korea should be divided along the 38th parallel, with Russia taking control of the north. But the Russians balked, and Japan consolidated its hold of Korea in 1910. After World War II, Japan relinquished control, and the U.S. State Department again looked to the 38th parallel to establish two separate countries. In 1950, North Korea invaded South Korea, launching the Korean War. Today, the demilitarized zone dividing the two countries intersects—but is not the same as—the 38th parallel.

The Korean War goes by many names.

In the United States, we call it “the Korean War” (and sometimes “the Forgotten War”). North Korea calls it “the Fatherland Liberation War.” In South Korea, it’s called “Six-Two-Five,” after the day it started. China’s subtle name for the conflict is “the War to Resist U.S. Aggression and Aid Korea.”

The Korean War provided an early victory for an American intelligence agency.

As I describe in my book Deep State: Inside the Government Secrecy Industry, the American intelligence community faced its worst fears on Friday, October 29, 1948. As post-war America was dismantling its signals intelligence and cryptanalysis capabilities, the Russians were digging in—and on “Black Friday,” as it was called, the Soviets activated a new communications grid and encryption methodology. Signals began transmitting by cable, cutting off most radio interceptions; what little remained was indecipherable. In response, the Secretary of Defense ordered the creation of an organization known as the Armed Forces Security Agency (AFSA).

Though AFSA suffered from institutional dysfunction and wasn’t particularly effective against the Soviets, it had good fortune during the Korean War, intercepting high-level North Korean broadcasts. To the astonishment of the agency’s signals-intelligence specialists, North Korea was broadcasting the details of its most sensitive military operations with little to no encryption at all. When the North Koreans finally got wise to America’s interception prowess, AFSA made short work of the new ciphers. Though not everyone was happy—according to the NSA’s history, leadership was upset that the decryptions weren’t at the level seen during WWII and the entire cryptological framework needed a shakeup, and the AFSA would eventually be reorganized as the National Security Agency [PDF].

The United States had dropped the Bomb only five years earlier, and was ready to do it again.

In 1950, the Bomb was only five years old and the wonder of the atomic age promised a bright nuclear future. It was just assumed that atomic weapons would be part of any future conflict—like the Korean War, for example. As the conflict dragged on, the Joint Chiefs of Staff authorized the employment of the atomic bomb against China if it sent troops or bombers into Korea. China ignored the threat. Likewise, there were plans to drop the Bomb on the Soviet Union if it got involved, but European leaders objected to such an escalation, fearing the Soviets would us it as a justification for the conquest of Europe. Accordingly, the United States promised to use atomic weapons in Korea only to prevent a “major military disaster.”

The Korean War never ended.

On July 27, 1953, American Lieutenant General William Harrison, Jr. and North Korean General Nam Il signed the Korean Armistice Agreement, ending “all acts of armed force” in Korea, until both sides were able to find a “final peaceful settlement.” The agreement was notably not a peace treaty, but rather, a ceasefire—and South Korea was not a signatory. Over 70 years later, it seems we are no closer to a peaceful ending of the conflict.

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This article originally appeared in 2013; it has been updated for 2025.