It is not possible to say with complete certainty which side fired the first shots, but it was obvious that the North Korean army was ready to attack and that immediately after the start of the war it invaded the 38th parallel in practically all parts of the border.
On June 25, 1950, the Korean War began, one of the largest and bloodiest Cold War-era conflicts. After World War II and liberation from the Japanese, Korea was under occupation by the USSR and American forces, with an agreed border at the 38th parallel. In time, two governments were formed in these two parts of the country, one communist and the other pro-Western, and both wanted power over the whole of Korea. Tensions lasted for years, until the open war began on that date. To date, it is not possible to say with complete certainty which side fired the first shots, but it was obvious that the North Korean army was ready to attack and immediately after the war invaded the 38th parallel in virtually all parts of the border.
In just three days, North Korean forces reached Seoul, the capital of South Korea, and managed to conquer it. This was also due to the fact that Seoul was in a rather unfavorable strategic position compared to the 38th parallel, practically in the immediate vicinity of North Korean territory. The United Nations declared the aforementioned North Korean invasion an invasion, giving the United States a kind of international legitimacy for military intervention. The war then lasted as long as 37 months, during which millions of people were killed (the number of soldiers killed was in the hundreds of thousands, and the number of civilians killed was even in the millions).