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Good morning.

Here’s what you need to know:

• Insults and threats.

Kim Jong-un, the North Korean leader, called President Trump a “mentally deranged U.S. dotard” (yes, it’s a word) today, adding, “ A frightened dog barks louder.” Here are Mr. Kim’s full remarks, a rejoinder to Mr. Trump’s calling him “Rocket Man.”

The president toughened sanctions on Thursday, and the North’s foreign minister spoke of responding with the largest-ever test of a hydrogen bomb in the Pacific. Our video explains how Pyongyang evades sanctions.