The U.S. will have spent almost $6 trillion on the war on terror by the end of fiscal year 2019, according to an annual report out Wednesday from Brown University's Watson Institute of International and Public Affairs.Between the lines: This differs from the Pentagon's calculation of $1.5 trillion because it includes more than Defense Department appropriations, such as costs of veteran care, interest on debt from the wars and war-related spending from the State Department.Go deeper:Afghanistan is by far America's longest warA look at the United States' never-ending wars in Afghanistan