While presidents have historically been the driving force behind foreign policy decision-making, Congress has used its constitutional authority to influence the process. The nation’s founders designed a system of checks and balances aimed at establishing a degree of equilibrium in foreign affairs powers. Though the president is the commander-in-chief of the armed forces and the country’s chief diplomat, Congress holds responsibility for declaring war and can also exert influence over foreign relations through its powers over taxation and appropriation, while the Senate possesses authority to approve or reject international agreements. This separation of powers compels the executive branch to work with Congress to achieve foreign policy goals, but it also sets up conflict over what policies best serve national interests and the appropriate balance between executive and legislative authority. Since the founding of the Republic, presidential power over foreign relations has accreted in fits and starts at the legislature’s expense. When core American interests have come under threat, legislators have undermined or surrendered their power by accepting presidents’ claims that defense of national interests required strong executive action. This trend peaked during the Cold War, when invocations of national security enabled the executive to amass unprecedented control over America’s foreign affairs.
