President Donald Trump bluntly warned North Korea against making any more threats to the U.S., saying the country “will be met with fire and fury like the world has never seen.”

Within hours of Mr. Trump’s comments, North Korea made its most specific threat against the U.S. yet. Through its official media, North Korea said it was considering firing missiles at Guam, a U.S. territory in the Pacific, and making the U.S. “the first to experience the might of the strategic weapons of the DPRK”—the Democratic People’s Republic...