Why North and South Korea are divided. A look into the split of Korea at the 38th parallel after World War II.
In 2018, a leader from North Korea crossed the Korean Demilitarized Zone for the first time ever to discuss long-awaited peace as well as denuclearization.
This was a historic moment for a number of reasons, however, it is only one event in a complicated, deeply rooted conflict that has lasted over seventy years.
Here is your brief guide on the Korean War, and the split at the 38th parallel.

A Unified Korea
For centuries before the division, the peninsula of Korea was unified, ruled by generations of dynastic kingdoms.
Between 1910 and 1945, Korea was under the control of the Japanese Empire, after a long integration process that began under the Japan-Korea Treaty of 1876, or the Treaty of Kanghwa. This treaty defined Korea as an independent state on an equal footing with Japan.
The aftermath of World War II, however, left Japan’s imperial possessions forfeited, and the United States and the Union of Soviet Socialist Republics (USSR), had to decide what to do with Korea. The two nations eventually opted to split the Korean peninsula, along the 38th parallel.
The Soviet Union decided to handle the north, and the United States would control the south.
By the end of the 1940s, however, the threat of communism was on the rise and the Cold War was in full swing. Together, tension plagued the newly formed Korean states that bordered each other.
Syngman Rhee (1875-1965), former anti-communist dictator in the south, and Kim Il Sung (1912-1994), a communist dictator in the north, both claimed to be the legitimate governing power of all of Korea.
The two dictators fought along the 38th parallel, with support from their allies: the United States in support of the south, and the USSR in support of the north. Rhee in the south, enjoyed the reluctant support of the American government, whereas Sung enjoyed the more enthusiastic support of the Soviets in the north.

Neither dictator was content in remaining on their side of the 38th parallel, as border skirmishes were common. Before the Korean War was even formally declared, nearly 10,000 soldiers were killed. With this said, however, the North Korean invasion came as an alarming surprise to American officials in 1950.
The Korean War
The Korean War officially began on June 25, 1950, when North Korea invaded South Korea. Backed by the Soviet Union and China, over 75,000 North Korean soldiers from the People’s Army went beyond the 38th parallel and engaged with South Korean forces. This invasion was the first military action of the Cold War.
As a response, the United Nations Security Council authorized aid for South Korea and dispatched forces immediately. By July, American troops entered the war on South Korea’s behalf. Overall, 21 countries contributed to the UN force, but primary and substantial support and resources came from the United States, which provided around 90% of the military personnel.

As far as American officials were concerned, U.S. efforts were against the forces of international communism itself. Officials and many people around the world feared that this invasion of North Korea was the first step in a communist campaign to take over the world.
Although the U.S. government never formally declared war, President Harry Truman issued a statement to Congress in June 1950, declaring:
“In these circumstances, I have ordered United States Air and Sea forces to give the Korean Government troops cover and support. The attack upon Korea makes it plain beyond all doubt that Communism has passed beyond the use of subversion to conquer independent nations and will now use armed invasion and war.”

After back-and-forth fighting across the 38th parallel, fighting eventually stalled and casualties mounted.
Finally, in July 1953, the Korean War came to an end. More than 5 million soldiers and civilians lost their lives in what many people in the United States refer to as “the Forgotten War,” for the lack of media attention it received as compared to more well-known wars and conflicts, like the Vietnam War, World War I, and World War II.
On July 27, 1953, both sides signed an armistice. A new boundary was drawn just north of the 28th parallel, and a two-mile-wide demilitarized zone (DMZ) between the two states was created.
Despite the longstanding ceasefire, no official peace treaty was ever signed.
Present Day
The Korean peninsula is still divided to this day. It has been for decades since 1953, as the Korean DMZ is still patrolled by troops and guarded with mines and artillery.