Eighteen years of war have strongly burdened the U.S. military. But climate change, refugee flows, and other destabilizing events will continue to heighten the risk of conflicts, at least some of which will require outside intervention to halt. The United States is still the only country with the capacity to intervene in conflicts around the globe, if it so chooses. Recruiting soldiers from around the world into a foreign legion, and granting U.S. citizenship to the legion’s veterans, as France does, can increase the U.S. willingness to use force abroad. It can also strengthen the link between citizenship and service in society, something Americans are already pondering given recent deportations of veterans.