The November 2024 presidential election has set the United States on a new course for national security and foreign policy. Vice President Kamala Harris, like President Joseph Biden before her, said she would have left untouched the United States’s role as the world’s policeman. Former President Donald Trump, more conscious of the high cost in lives and treasure of carrying this burden, seeks to align means and ends, and reduce America’s global commitments.
But Trump’s victory does not necessarily portend more, rather than less, American involvement in foreign wars. Under the Biden administration, the United States poured billions of dollars and military equipment to support the defense of Ukraine against Russian invasion. While it meddled in Israel’s tactics, Biden still supported the Netanyahu government’s war against Hamas in Gaza, Hezbollah in Lebanon, and their Iranian supporters. President Trump experienced relative peace during his four years in office, but he still used force against Syria for using chemical weapons, Russian mercenaries in the Middle East, and the Iranian Revolutionary Guard Corps by killing its leader, General Soleimani. While Trump has called for an end to the war in Ukraine, he has also supported an acceleration of the war between Israel and its enemies in Gaza, Lebanon, and Iran.
Fearful of the prospect of more “endless wars,” members of the new Congress may attempt to rein in presidential warmaking. A bipartisan coalition, for example, has attempted to repeal the 2001 and 2002 Authorizations to Use Military Force, which supported President George W. Bush’s response to the 9/11 attacks and his invasion of Iraq (both of which I helped draft—more on that below). “Three Presidents, both Republicans and Democrats, have used this permission to drag out conflicts that will get us into new ones,” Rep. Nancy Mace (R.-S.C.) said during a failed 2021 try. These critics of foreign wars argue that the president cannot launch offensive military operations without the approval of Congress, thanks to the Constitution’s vesting in the legislative branch “the Power … to Declare War.”
The view that Congress must authorize foreign wars may be widespread, but it is dangerously mistaken. Congressional support, of course, can signal political unity in war to both friends and enemies. But it is neither constitutionally necessary nor functionally wise—if Congress wishes to control warmaking, it has the power of purse and an ample set of tools available. Neither presidents nor Congresses have acted under the belief that the Constitution requires a declaration of war before the U.S. can conduct military hostilities abroad. The United States has used force abroad more than 100 times, but it has declared war in only five cases: the War of 1812, the Mexican-American and Spanish-American Wars, and World Wars I and II.
Presidents alone have sent the U.S. Armed Forces into combat from the nation’s earliest days. They ordered troops to battle Indians in the West, Barbary pirates (who were really princes within the Ottoman Empire) in the Mediterranean, and revolutionaries in Russia. Without any declaration of war, Presidents Truman and Eisenhower sent troops into conflict with communists in Korea, while Presidents Kennedy, Johnson, and Nixon oversaw an undeclared war in Vietnam. American troops have fought abroad to engineer regime changes in South and Central America and to prevent human rights disasters in Somalia and the Balkans. Other conflicts, such as the 1991 Persian Gulf War, the 2001 invasion of Afghanistan, and the 2003 Iraq War, received legislative “authorization” but not declarations of war. The practice of presidential initiative, followed by congressional acquiescence, has spanned both Democratic and Republican administrations and reaches back from President Biden to Presidents Abraham Lincoln, Thomas Jefferson, and George Washington.
Common sense does not support replacing the way our Constitution has worked in wartime with a radically different system that mimics the peacetime balance of powers between president and Congress. If the issue were energy use or entitlement reform, Congress would enact policy first and the president would faithfully implement it second. But the Constitution reverses the polarity of our system in foreign affairs and war. Our Framers decided that the president would take the initiative in matters of national security while Congress would check the executive with its power of the purse.
Critics of the presidency, however, believe that the Founding’s anti-monarchical spirit dictates reading the Constitution to limit executive war powers. If the Framers rebelled against King George III’s repressions, surely they would not give the president much authority. It is true that the revolutionaries rejected the royal prerogative, and their new state governments experimented with weak governors and powerful assemblies. Legislatures chose their governors, who were often limited to one- or two-year terms and forbidden from re-election. Americans also turned a skeptical eye toward a central government made powerful by a permanent military establishment funded through oppressive taxation. The Articles of Confederation gave Congress the power to make war and peace, but it forced the national government to beg the states for men, material, and money.
This Revolutionary history can be misleading. It may cause some to ignore the fundamental difference in the Constitution’s treatment of domestic and foreign affairs. When the Framers wrote the Constitution in 1787, they rejected these failed state experiments in constitutional government and revived an independent, unified chief executive with its own powers in national security and foreign affairs. Their most important choice was to make the president the commander-in-chief of the armed forces and to vest in his office all of the executive power of the federal government. As Alexander Hamilton wrote in Federalist No. 74: “The direction of war implies the direction of the common strength, and the power of directing and employing the common strength forms a usual and essential part in the definition of the executive authority.” Presidents should conduct war, he wrote, because they can act with “decision, activity, secrecy, and dispatch.” In perhaps his most famous words, Hamilton wrote (Federalist No. 70): “Energy in the executive is a leading character in the definition of good government. … It is essential to the protection of the community against foreign attacks.”
The writings of Machiavelli, Hobbes, Locke, and Blackstone may have influenced them, but, more importantly, the Framers had learned the lessons of history. They understood that foreign affairs are unpredictable and involve the highest of stakes, making them unsuitable to regulation by pre-existing legislation. Foreign affairs can demand swift, decisive action, sometimes under pressured or emergency circumstances, that is best carried out by a branch of government that does not suffer from multiple vetoes or disagreements. Legislatures are too large and unwieldy to take the swift and decisive actions required to defend the nation or conduct war. Our Framers replaced the Articles of Confederation, which had failed in part because it had no unified executive, with the Constitution’s single president for precisely this reason. Even when it has access to the same intelligence as the executive branch, Congress’s loose, decentralized structure would paralyze American policy while foreign threats grow.
Congress has no political incentive to mount and see through its own wartime policy. Members of Congress, who are interested in keeping their seats at the next election, do not want to take stands on controversial issues where the future is uncertain. They will avoid like the plague any vote that will anger large segments of the electorate. They prefer that the president take the political risks and be held accountable for failure.
As a former Senate aide and later a Justice Department official in 2001–2003, I saw this firsthand. I helped draft the 2001 Authorization to Use Military Force (AUMF) in the wake of the 9/11 attacks that empowered the President “to use all necessary and appropriate force against those nations, organizations, or persons he determines planned, authorized, committed, or aided the terrorist attacks that occurred on September 11, 2001.” The 2001 AUMF did not limit its approval to a place or a time, such as to a specific region or for a set number of years but offered the President open-ended authority to pursue those responsible for the 9/11 attacks all over the world. As a Justice Department official, I maintained that the President needed no authority from Congress to defend the nation. But President George W. Bush welcomed Congress’s political support and so we at DOJ and the White House drafted the AUMF—not Congress. When we sat down to negotiate over the draft, congressional leaders made virtually no changes to the text—they wanted to be able to claim later (as they did) that they had no responsibility for an armed conflict to come that might become unpopular.
I witnessed a similar dynamic at work with the Iraq War. As the United States moved toward war against Iraq in the fall of 2002, President Bush decided again to seek the support of Congress. At the Justice Department, we believed that the President did not lack constitutional authority to attack Iraq, but we set to work drafting another AUMF. I remember briefing a senior senator, who was complaining that the White House was making him take a vote on Iraq that he didn’t want to take, and then asked the meaning of specific phrases. As a former Judiciary Committee aide myself, I had to remind him that the Senate excelled at not voting on anything it didn’t want to, and further that it was up to Congress to decide on the meaning of the AUMF’s text. I suggested that the senator offer amendments with more specific definitions, to which he responded with a face that must have approached horror. The last thing he wanted, he said, was his fingerprints anywhere on the text of the AUMF—it would make him responsible for the course of the Iraq War later. Even though the House passed the AUMF 296-133, and the Senate by 77-23, the support of Members of Congress became scarce when the Iraq War ran into hardships in Bush’s second term.
Congress’s track record when it has opposed presidential leadership has not been a happy one. Perhaps the most telling example was the Senate’s rejection of the Treaty of Versailles at the end of World War I. Congress’s isolationist urge kept the United States out of Europe at a time when democracies fell and fascism grew in their place. Even as Europe and Asia plunged into war, Congress passed Neutrality Acts designed to keep the United States out of the conflict. President Franklin Roosevelt violated those laws to help the Allies and prepare the nation into war against the Axis. While pro-Congress critics worry about a president’s foreign adventurism, the more dire threat to our national security may come from passivity and inaction, rather than from activity and aggressiveness.
Many point to the Iraq and Vietnam Wars as examples of the faults of the “imperial presidency.” Neither war, however, could not have continued without the consistent support of Congress. Congress authorized hostilities in Southeast Asia in the Tonkin Gulf Resolution, and it enacted an Authorization to Use Military Force in 2002 for Iraq. But even more significantly, Congress opened the purse to raise and fund the large military forces necessary to conduct the wars. And Vietnam ushered in a period of congressional dominance that led to the passage of the ineffectual War Powers Resolution and accepted a series of American setbacks in the Cold War. Congress passed the Resolution in 1973 over President Nixon’s veto, and no president, Republican or Democrat, has accepted the constitutionality of its 60-day limit on the use of troops abroad. No federal court has ever upheld the resolution. Even Congress has never enforced it.
Despite the record of practice and the Constitution’s institutional design, critics nevertheless argue for a radical remaking of the American way of war. They typically base their claim on Article I, Section 8, of the Constitution, which gives Congress the power to “declare War.” But these observers read the eighteenth-century constitutional text through a modern lens by interpreting “declare War” to mean “start war.” When the Constitution was written, however, a declaration of war served diplomatic notice about a change in legal relations between nations. It had little to do with the domestic constitutional process for launching hostilities. In the century before the Constitution, for example, Great Britain—where the Framers borrowed the phrase “power to declare War”—fought numerous major conflicts but declared war only once beforehand. By the time of the Constitution’s ratification, Hamilton could observe in Federalist No. 25 that “the ceremony of a formal denunciation of war has of late fallen into disuse.”
Our Constitution sets out specific procedures for passing laws, appointing officers, and making treaties. There are none for waging war, because the Framers expected the president and Congress to struggle over war through politics, not law. Other parts of the Constitution support this reading. Article I, Section 10, for example, mandates that the states shall not “engage” in war “without the consent of Congress” unless “actually invaded, or in such imminent Danger as will not admit of delay.” This provision creates exactly the limits desired by anti-war critics, complete with an exception for self-defense. Notice that the Constitution here uses “engage” in war, not “declare” war to refer to launching hostilities. If the Framers had wanted to require congressional permission before the president could wage war, they simply could have repeated this provision and applied it to the executive.
Presidents do not have complete freedom to take the nation to war. Congress has ample powers to control presidential policy. Under Article I, Section 8 of the Constitution, only Congress can raise the military, which gives it the power to block, delay, or modify war plans. Before 1945, for example, the United States had such a small peacetime military that presidents who started a war would have to go hat in hand to Congress to build an army and navy to fight it. Since World War II, it has been Congress that has authorized and funded our large standing military, one primarily designed to conduct offensive, not defensive, operations (as we learned all too tragically on 9/11) and to swiftly project power worldwide. If Congress wanted to discourage presidential initiative in war, it could build a smaller, less offensive-minded military.
Congress’s check on the presidency lies not just in the long-term raising of the military. It can also block any immediate armed conflict through the power of the purse. If Congress feels it has been misled in authorizing war, or it disagrees with the president’s decisions, all it need do is cut off funds, either all at once or gradually. It can reduce the size of the military, shrink or eliminate units, or freeze supplies. Using the power of the purse does not even require affirmative congressional action. Congress can just sit on its hands and refuse to pass a law funding the latest presidential adventure, and the war will end quickly. Congress need not even risk a presidential veto; it can simply decline to enact the funds needed to keep a war going. Even the Kosovo war, which lasted little more than two months and involved no ground troops, required special funding legislation.
The Framers expected Congress’s power of the purse to serve as the primary check on presidential war. During the 1788 Virginia ratifying convention, Patrick Henry attacked the Constitution for failing to limit executive militarism. James Madison responded: “The sword is in the hands of the British king; the purse is in the hands of the Parliament. It is so in America, as far as any analogy can exist.” Congress ended America’s involvement in Vietnam by cutting off all funds for the war. It did the same to prevent President James Polk for pursuing even grander aims in the Mexican-American War of 1846–1848.
Our Constitution has succeeded because it favors swift presidential action in war, checked by Congress’s funding power. If a president continues to wage war without congressional authorization, as in Libya, Kosovo, or Korea, it is only because Congress has chosen not to exercise its easy check. If Congress wants to prevent future presidents from waging wars abroad, it can re-orient the U.S. military away from its expeditionary focus. Congress need not fund the Navy’s carrier battle groups, which serve as portable air bases to station off the shore of hostile enemies. It need not provide the Army with a worldwide network of large bases, expensive overseas deployments, and offensive weapons systems. But Congress instead funds an expeditionary military designed to fight offensive wars abroad, rather than one aimed at homeland and hemispheric defense. Rather than presidential adventurism, the story of the last 80 years has been one of cooperation between the branches of government in pursuing a hegemonic role in defending the West. We should not confuse Congress’s desire to escape political responsibility for military setbacks as a defect in the Constitution.
A radical change in the system for making war might appease critics of presidential power. But it could also seriously threaten American national security. In order to forestall another 9/11 attack, or to take advantage of a window of opportunity to strike terrorists or rogue nations, the executive branch needs flexibility. It is not hard to think of situations where congressional consent cannot be obtained in time to act. Time for congressional deliberation, which can lead to passivity and inaction, will come at the price of speed and secrecy.
The Constitution creates a presidency that can respond forcefully to prevent serious threats to our national security. Presidents can seize the initiative while Congress can check them with its power of the purse. Instead of imposing a legalistic process, the Framers left war to politics. As we confront the new challenges posed not just by terrorism, rogue nations, and WMD proliferation, but the return of great power rivalry, the president must take the initiative to protect the nation’s security, ideally with the support of Congress, but alone if necessary.
John Yoo is a Distinguished Visiting Professor, School of Civic Leadership, University of Texas at Austin; Emanuel S. Heller Professor of Law, University of California at Berkeley School of Law; Nonresident Senior Fellow, American Enterprise Institute.
