America’s contemporary security state—a massive bureaucracy staffed with military and civilian experts—is a dominant feature in current debates over national security policy. Few decisions regarding war and diplomacy are made without consulting executive branch experts. While many contend that the current national security bureaucracy is an outgrowth of the National Security Act of 1947 (NSC), the origins of national security expertise as a concept date back to the founding. The Founders recognized that “energy in the executive” was a key element of good government and early drafts of the Constitution even referred to a cabinet-style government which would include a Department of Foreign Affairs and a Department of War. After the founding the nation debated the propriety of secret presidential advisers, sole Presidential conduct of foreign affairs, the dividing line between matters of peace and matters of war, and the propriety of executive branch agencies created, staffed, and exercising powers at the discretion of the president and subject only to his authority and expertise. The nation’s experiences during the Civil War, during the beginning of the industrial age, and during World War I each incrementally changed the nation’s understanding of founding era ideas regarding national security expertise. This Article traces those historical developments, ties them to founding era debates and contemporary affairs, and argues that scholarly discourse about authority is oftentimes inextricably tied to debates over national security expertise.