The Korean War is an escalation of border clashes between two rival Korean regimes, each of which is supported by external powers, with each trying to topple the other through political and conventional tactics.

In a very narrow sense, some may refer to it as a civil war, though many other factors are at play.

After failing to strengthen their cause in the free elections held in South Korea during May 1950 and the refusal of South Korea to hold new elections per North Korean demands, the communist North Korean Army assaults the South on June 25, 1950.

The conflict is then expanded by the United States and the Soviet Union's involvement as part of the larger Cold War.

The main hostilities are during the period from June 25, 1950 until the armistice (ceasefire agreement) is signed on July 27, 1953.In South Korea, the war is often called 6·25 or 6·25 War, from the date of the start of the conflict or, more formally, Hanguk Jeonjaeng (Korean: literally "Korean War").

In North Korea, while commonly known as the Korean War, it is formally called the Jogug Gaebang Jeonjaeng or Fatherland Liberation War.

In the United States, the conflict is officially termed a police action — the Korean Conflict — rather than a war, largely in order to avoid the necessity of a declaration of war by the U.S. Congress.

The war is sometimes called The Forgotten War or The Unknown War because it is a major conflict of the 20th century that gets far less attention than the Second World War, which preceded it, and the Vietnam War, which succeeds it.

Ironically, the war is a unique combination of the techniques utilized in both World Wars, beginning with swift, fast-paced infantry advances following well-choreographed bombing raids from the air.

However, following both sides' failures at holding the land captured, battles quickly evolve into First World War-type trench warfare in January 1951, lasting until the essential border stalemate at the end.

In China, the conflict is known as the War to Resist America and Aid Korea, but is today commonly called the "Korean War".