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On Monday, President-elect Donald Trump waded into the morass of U.S. policy on North Korea's ambitions to become a nuclear power, an issue that has vexed U.S. presidents since at least the Eisenhower administration but has become more pronounced since Pyongyang's first successful nuclear weapons test in 2006. Trump was responding to North Korean leader Kim Jong Un's pronouncement on Sunday that his country is in the final stages of testing an intercontinental ballistic missile that could reach the U.S., and the president-elect's message just fit within Twitter's 140-character limit: "North Korea just stated that it is in the final stages of developing a nuclear weapon capable of reaching parts of the U.S. It won't happen!"

In a follow-up tweet, sent about an hour later, Trump did not provide any details but instead chided China for both selling America consumer goods and failing to rein in its troublesome neighbor:

You can learn more about Trump's 140-character nuclear diplomacy, including the real fact that "China didn't immediately respond to Trump's tweets," in the Wall Street Journal video below. Peter Weber