On Sept. 11, terrorists fly two planes into New York’s World Trade Center and a third into the Pentagon. A fourth hijacked plane crashes in Pennsylvania. In all, 2,996 were killed. The attack ushers in a new era of war, with American men and women volunteering to bring the fight to the enemy. American troops will continue to serve in Afghanistan, Iraq, Yemen, Somalia, Syria, and other countries in support of the “War on Terror.”