The North Korean regime, eager to deter any attempt by a latter-day Gen. MacArthur to invade the nation and overthrow it, has been stockpiling weapons of mass destruction for decades. Back in 1997, a North Korean army defector told a U.S. Senate subcommittee that the regime had amassed an arsenal that included 5,000 tons (4,536 metric tons) of toxic gas and two or three nuclear warheads, which it was poised to use against U.S. forces. In 2006, Kim Jong Il confirmed that information by staging a test explosion of a nuclear weapon [source: Bowden].
Since then, North Korea has staged several more successful nuclear tests, and its arsenal has grown to between 13 and 30 nuclear weapons, according an April 2017 presentation by David Albright, a former United Nations weapons inspector who now heads the Institute for Science and International Security.
But just because North Korea has nukes, it doesn't necessarily mean that it could use them to attack the U.S. tomorrow. In his presentation, Albright also noted there are reasons to doubt that North Korea has the ability right now to build a nuclear device that will fit atop an ICBM and survive re-entry through Earth's atmosphere so that it can explode over a U.S. city.
But that provides scant comfort. In 2015, another analyst, Jeffrey Lewis of the East Asia Nonproliferation Program at the James Martin Center for Nonproliferation Studies, noted that the North Koreans probably already had the ability to build a miniaturized nuke, but the question was whether the warhead would remain stable upon re-entry or veer off target and perhaps explode over San Jose instead of San Francisco. "That's a problem, of course, but Kim Jong Un might be content with such an outcome," he wrote in the political journal 38 North.