The U.S. awoke Friday morning to news that North Korea has set off its largest-ever nuclear weapon test explosion. The 10-kiloton detonation—the country’s second this year and fifth since 2006—follows its launch of three ballistic missiles toward the Sea of Japan earlier this week and is North Korea’s first atomic explosion since it put a satellite into orbit in February. What all of this means for the rest of the world’s security—South Korea’s and Japan’s in particular—is anyone’s guess. The ramping up of ongoing nuclear and ballistic missile tests, however, feeds growing concerns that Kim Jong-un’s regime will soon be able to make good on its threats to target parts of the U.S. as well as Washington’s allies in the region.

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