Japan is lending a hand to the U.S. Navy as it tries to pressure North Korea.
The Japanese navy is sending its largest warship, the Izumo, to escort a U.S. supply ship heading toward the Korean Peninsula. That U.S. ship is refueling a fleet in the area.
The Izumo is only protecting the American ship within Japanese waters, but it's still a big break from tradition for the nation's military.
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Since the end of WWII, Japan has only been able to act in self-defense. This is the first military movement under a new Japanese law that allows its ships to come to the defense of an ally that's protecting Japan.
American ships were sent to the Korean Peninsula to act as a deterrent. But the North launched another failed ballistic missile test on Saturday –– its fourth since March.
Japan's prime minister called the latest missile launch a "grave threat" to his country.
