It is not difficult to imagine

It is not difficult to imagine how this scenario [war with North Korea] could come to pass. ... Imagine that Kim and Trump arrive at the summit only to discover that they hold radically different views of the commitment to "denuclearize": Trump believes that Kim is willing to negotiate away his arsenal for sanctions relief, whereas Kim believes that full denuclearization also requires the removal of U.S. troops from the Korean Peninsula and and end to the U.S.-South Korean alliance... . After it becomes clear that Trump will not move forward on Kim's terms, Kim is outraged and renews his August 2017 pledge to test missiles over Guam.

Both Washington and Pyongyang now think the other is responsible for derailing diplomacy. Out of a desire to induce the United States to drop its denuclearization demands, Kim decides to show that his willingness to negotiate does not mean his will has been broken, and he proceeds with his missile launch. Much as the Japanese did before they attacked Pearl Harbor, he hopes that a missile test over Guam - a U.S. territory but not a state - will unnerve the United States enough to persuade it to accept his nuclear program, but not so much as to bring a full-scale war.

But then, one of his missiles expels debris over Guam. Fragments from the reentry vehicle strike the island itself, killing a few residents - who are, after all, U.S. citizens. Trump declares this "an act of war" and gives Kim 48 hours to issue a formal apology and a pledge to denuclearize. Kim does not comply, and the United States dusts off one of its plans for a limited military strike. It attacks a known missile storage facility, believing the limited nature of the target will induce Kim's cooperation and minimize the risk of retaliation. Instead, Kim views the strike as the beginning of a larger effort to disarm him and as a prelude to regime change. Following his conventional bombardment of Seoul, the United States begins to attack other known weapons sites and command-and-control facilities to neutralize the threat. Kim launches nuclear weapons the following day.

- from "Perception and Misperception on the Korean Peninsula," Robert Jervis and Mira Rapp-Hooper, in Foreign Affairs, May/June 2018, pg. 116