Congress declares war by passing a joint resolution through both the House and Senate by simple majority and presenting it to the President for signature. The Constitution places this power with the legislative branch alone under Article I, Section 8, Clause 11, which gives Congress the power “to declare War.”1Congress.gov. Article I Section 8 Clause 11 The process follows the same path as any other joint resolution, but its weight makes every step more visible. Congress has issued only 11 formal declarations across five conflicts, and the last one came in 1942.
Where the Power Comes From
Article I, Section 8, Clause 11 gives Congress authority to “declare War, grant Letters of Marque and Reprisal, and make Rules concerning Captures on Land and Water.”2Congress.gov. ArtI.S8.C11.1.1 Overview of Congressional War Powers The Framers made this choice deliberately. An early draft gave Congress the power to “make war,” and the Convention changed it to “declare war” so the President could still respond to a sudden attack without waiting for a vote.3Cornell Law Institute. U.S. Constitution Annotated Article I Section 8 Clause 11 – Declarations of War
Article II names the President as Commander in Chief, but that title was meant to keep the military under civilian control, not to hand the executive the power to start a war. Scholars who read the clause narrowly argue it gives the President no authority beyond directing forces Congress has already authorized.4Legal Information Institute. Commander in Chief Powers The tension between these two provisions runs through every major military action in American history, but the text on declaring war itself is clear: the decision belongs to Congress.
The Four Steps
A formal declaration of war moves through the same legislative pipeline as any joint resolution. Historically, though, Congress has compressed weeks of ordinary procedure into a matter of days when the moment called for it.
The President Requests It
Every formal declaration in American history has begun with the President addressing a joint session of Congress and making the case. These addresses identify the hostile government, explain why diplomacy failed, and describe the threat. The speech itself carries no legal weight. It’s an invitation for Congress to exercise a power the President does not hold.
Committees Review the Resolution
Once a joint resolution is introduced, it goes to the House Committee on Foreign Affairs and the Senate Committee on Foreign Relations. The House committee’s jurisdiction covers “war powers, treaties, executive agreements, and the deployment and use of United States Armed Forces.”5House Foreign Affairs Committee. Jurisdiction The Senate committee’s jurisdiction explicitly includes “intervention abroad and declarations of war.”6Senate Foreign Relations Committee. SFRC Jurisdiction Members review the resolution’s language, receive classified briefings, and vote on whether to send it to the full chamber.
Both Chambers Vote
After each committee reports the resolution, the House and Senate schedule floor debate and a vote. A declaration of war requires only a simple majority in each chamber. There is no constitutional supermajority requirement, and neither chamber gives war resolutions any special procedural privilege. They move under the same rules as ordinary legislation unless the leadership agrees to expedite them.
Both chambers must pass identical text. If the versions differ, they reconcile the language through amendments or a conference committee before anything can go to the President. In the 19th century, Congress passed declarations as bills; starting with World War I, every declaration has taken the form of a joint resolution.7EveryCRSReport.com. Declarations of War and Authorizations for the Use of Military Force – Historical Background and Legal Implications
The President Signs It
Once both chambers pass identical text, the resolution goes to the President under the Presentment Clause of Article I, Section 7. The signature turns the resolution into law.8Constitution Annotated. U.S. Constitution Article I Section 7 Clause 2 – Role of President A President could, in theory, veto a declaration, and Congress could override with a two-thirds vote in both chambers. It has never happened. In every case, the President asked for the declaration in the first place. After signing, the law is sent to the Office of the Federal Register for publication.9National Archives. Public Laws At that point, the United States is formally at war under both domestic and international law.
What a Declaration Actually Does
A formal declaration is not only a political statement. It flips legal switches across the federal code that stay dormant in peacetime and remain dormant even when Congress authorizes military action by other means.
The Alien Enemy Act of 1798 lets the President detain, restrict, or remove nationals of a hostile foreign government who are 14 or older and living in the United States. The authority activates automatically whenever “there is a declared war between the United States and any foreign nation or government” and the President issues a public proclamation.10Office of the Law Revision Counsel. 50 U.S. Code 21 – Restraint, Regulation, and Removal
The Trading with the Enemy Act blocks nearly all commerce with an enemy nation and its nationals during wartime without a presidential license. That covers financial transactions, imports, exports, and even personal communications, and it gives the President authority to regulate foreign exchange, seize enemy-owned property, and control the movement of currency and securities.11Office of the Law Revision Counsel. 50 USC Chapter 53 – Trading With the Enemy
Beyond those two statutes, a declaration triggers standby authorities across military personnel regulations, defense production, foreign intelligence surveillance, criminal law, insurance contracts, agricultural exports, tort claim deadlines, and congressional budget procedures. Many of those powers can also be reached through a declared national emergency, which is one reason presidents have often preferred that route. A formal declaration of war is the only instrument that activates all of them at once without any further presidential action.12Naval History and Heritage Command. Declarations of War and Authorizations for the Use of Military Force
The 11 Declarations on the Books
Congress has declared war 11 times against 10 countries, all within five conflicts:13U.S. Senate. About Declarations of War by Congress
- War of 1812: Great Britain, June 18, 1812
- Mexican-American War: Mexico, May 13, 1846
- Spanish-American War: Spain, April 25, 1898
- World War I: Germany, April 6, 1917; Austria-Hungary, December 7, 1917
- World War II: Japan, December 8, 1941; Germany and Italy, December 11, 1941; Bulgaria, Hungary, and Romania, June 5, 1942
The speed of some of these votes is striking. The day after Pearl Harbor, the Senate voted 82–0 and the House 388–1 to declare war on Japan. Three days later, after Germany and Italy declared war on the United States, Congress responded with unanimous votes in both chambers.7EveryCRSReport.com. Declarations of War and Authorizations for the Use of Military Force – Historical Background and Legal Implications
Why It Hasn’t Happened Since 1942
Korea, Vietnam, the Gulf War, Afghanistan, and Iraq were all fought without a formal declaration. That does not mean Congress stopped authorizing military force. It shifted to a different tool: the Authorization for Use of Military Force, or AUMF.
An AUMF gives the President legal authority to use force but doesn’t activate the domestic standby statutes a declaration does, and it doesn’t create a legal state of war under international law. Congress can calibrate how much power it hands over. The 2001 AUMF, passed three days after September 11, authorized the President “to use all necessary and appropriate force” against those responsible for the attacks and stated that it was “specific statutory authorization” for purposes of the War Powers Resolution.14Congress.gov. Public Law 107-40 – Authorization for Use of Military Force It did not, however, flip the switches that a declaration of war would have.
The War Powers Resolution of 1973, passed over President Nixon’s veto, sits alongside this framework. It says the President may introduce armed forces into hostilities only under a declaration of war, a specific statutory authorization, or a national emergency created by an attack on the United States, and it requires notification of Congress within 48 hours and withdrawal within 60 days if Congress does not authorize the deployment.15Office of the Law Revision Counsel. 50 USC 1541 – Purpose and Policy Every president since Nixon has questioned whether it constitutionally binds the Commander in Chief, but none has openly refused to file the reports.
The formal declaration process is still available. Congress simply hasn’t used it since 1942, in part because the modern alternatives let it authorize force without triggering the full wartime legal machinery that a declaration would switch on.