Congress made history this week by passing a resolution that cuts off U.S. support for Saudi-led forces in the civil war in Yemen. This is the first time since Congress originally passed the War Powers Resolution in 1973 that we have used it to call on the president to withdraw from an undeclared war. The passage of this resolution has implications far beyond Yemen and opens a much broader and extremely important debate about how and when the United States uses our military, and who must authorize that use. According to a recent study by the Costs of War Project at Brown University, the War on Terror will have cost American taxpayers almost $5 trillion through Fiscal Year 2019. When taking in to account future health care obligations for veterans injured in post-9/11 wars, the bill comes closer to $6 trillion. Even after this enormous expense, the world has more militants, not fewer. A November 2018 report from the Center for Strategic and International Studies found that the number of militants has continued to grow. "Despite nearly two decades of U.S.-led counterterrorism operations," the report said, "there are nearly four times as many Sunni Islamic militants today as there were on September 11, 2001." The time is long overdue for Congress to reassert its constitutional responsibility over war making. We need a serious national debate over when and where we put our military in harm's way. Congress's historic vote on Yemen this week is an important beginning in that process, now we must continue forward.