Wars between nations face persistent escalation risk, decades of conflict data suggest

Military leaders frequently underestimate how big the wars they engage in will get. Gen. Douglas MacArthur predicted U.S. troops could come home from the Korean War in time for Christmas, just months after the conflict started. But Chinese attacks that winter extended the war for years. And President Donald Trump said in March that the Iran war would be a "short-term excursion," but it has now lasted more than five months, with periods of escalation.