Kim Il Sung

5 things to know about N. Korean leader's rebuke of Trump

On the surface it seems like more of the same: North Korea responds to another threat by U.S. President Donald Trump by calling him a "deranged" old man who will "pay dearly" for his insults.

These words, however, carry the weight of an unprecedented personal rebuke from North Korea's supreme leader, Kim Jong Un.

Behind Kim's colorful language released Friday is a remarkable window into the thinking — albeit filtered through state media — of the leader of a country that, despite opposition by the world's sole superpower, stands on the brink of nuclear weapons mastery.

Here are five things to know about Kim Jong Un's statement: