The United States national-security establishment is vast, yet the United States has failed to meet its initial objectives in almost every one of its major, post-World War II conflicts. Of these troubled efforts, the US wars in Vietnam (1965-73), Iraq (2003-11), and Afghanistan (2001-present) stand out for their endurance, resource investment, human cost, and miscalculated decisions. Because overarching policy goals are distant and open to interpretation,...