Nearly 70 years ago, the Korean peninsula, once a unified nation, split into two distinct states. In the resulting Korean War (1950 – 1953), millions of people were killed. But the peninsula remained divided, separated by a cease-fire line known as the Demilitarized Zone (DMZ). In the decades that followed, North Korea became an increasingly isolated, totalitarian state. Despite today being one of the poorest nations on earth, North Korea has developed a huge military and a nuclear arsenal, and has repeatedly threatened to attack the United States. This lesson explores the history of the Korean peninsula and how North Korea became the rogue state it is today.