University of Southern California professor David Kang looks back over the past seven decades of history on the Korean Peninsula with NPR's Lulu Garcia-Navarro.

LULU GARCIA-NAVARRO, HOST: The leaders of North and South Korea will meet face-to-face this week. Ahead of the summit, Kim Jong Un announced that North Korea will stop its missile tests and close its nuclear test sites, and there's now a direct telephone hotline set up between the two leaders on the peninsula. This is a surprising development for two countries whose conflict has seemed intractable.

DAVID KANG: The tragedy of the Korean peninsula is that it's the only place in the globe where the Cold War still exists.

GARCIA-NAVARRO: That's David Kang. He's a professor of International Relations and Business at the University of Southern California.

KANG: Nothing has essentially changed since 1945. We are in the same place we were with two regimes nose-to-nose.

GARCIA-NAVARRO: It's a complicated history that involves not just the North and the South but also China, Russia, Japan and the United States. And this morning, we're going to delve into how we got here.

KANG: Korea had been one political unit from the Yalu River down to the southern part of the peninsula for about 1300 years - had been one country.

GARCIA-NAVARRO: That would change after World War II and a fateful agreement made between the U.S. and the Soviet Union - two allies that would become enemies. Japan was in control of the whole peninsula when it was defeated by the Allied forces. ...