Article I of the Constitution assigns to Congress the authority to declare. Congress exercised this authority in 1812, declaring war against Britain.
James Madison, president at the time and of course the chief architect of the Constitution, had been careful not to intrude on congressional prerogative in the matter of war. In June 1812 Madison sent Congress a message detailing British insults to American honor, depredations on American trade and violations of American and international law. Yet Madison stopped short of an explicit request for a war declaration. He let Congress draw its own conclusions from the case he had made.
Congress did, and it concluded that war was necessary. Yet the votes on the war declaration were hardly overwhelming: 19 to 13 in the Senate, 79 to 49 in the House.
James Polk, the youngest president to date, might not have been aware of the votes when they were taken. Polk was sixteen in 1812. But he was aware of them when he considered war against Mexico in 1846. Though Congress had formally declared only the one war, against Britain, American forces had gone into battle several times. George Washington ordered action against Indians in Ohio. John Adams launched an undeclared naval war—the “Quasi-war”—against France. Madison approved reprisal raids against Creek Indians in Mississippi. James Monroe covertly instructed Andrew Jackson to invade Spanish Florida. Jackson as president directed the Black Hawk war in Illinois and Michigan. Jackson, Martin Van Buren, William Henry Harrison and John Tyler conducted war against the Seminole Indians in Florida.
In none of these cases did Congress declare war. The principal reason was that war was generally understood to be a conflict between sovereign nations. Congress and the presidents preferred not to treat Indian tribes as sovereign nations, a status that would have raised numerous political and ethical difficulties. The Supreme Court went along, calling the tribes “domestic dependent nations.”
Polk at first didn’t want war with Mexico. What he wanted was California, at that time part of Mexico. Polk was completing an agreement with Britain over the Oregon country, which pushed America’s northwestern frontier to the Pacific. He wanted the southwestern frontier to reach the Pacific as well. He offered to purchase California from Mexico.
But Mexican officials, chafing from what they deemed America’s theft of Texas, refused to entertain Polk’s offer.
Polk pressed the matter. He sent U.S. troops to southern Texas, where the border with Mexico was in dispute. Polk said the border was the Rio Grande. Mexico said it was the Rio Neuces, a hundred miles north of the Rio Grande. Rather than negotiate the matter, Polk aggravated it. He ordered General Zachary Taylor to occupy the disputed strip. Polk hoped Mexican troops would challenge the occupation. A fight would ensue, and Polk would be able to say American blood had been shed on American soil.
The Mexican forces refused to oblige. They remained south of the Rio Grande.
Polk’s frustration grew. He went so far as to draft a request to Congress for a war declaration, magnifying diplomatic differences into intolerable aspersions on American honor.
He was at the point of sending the request to Congress when a message arrived from Texas. The fight Polk had tried to provoke had finally occurred. “After reiterated menaces, Mexico has passed the boundary of the United States, has invaded our territory and shed American blood upon the American soil,” the president said. “The two nations are now at war.” Polk had no choice. “I invoke the prompt action of Congress to recognize the existence of the war, and to place at the disposition of the Executive the means of prosecuting the war with vigor.”
Polk got his war declaration. Even members of Congress distrustful of Polk felt obliged to answer the killing of eleven American soldiers and capture of fifty-two with votes in favor of war.
Polk got California. After a war fought mostly in Mexico proper and which culminated in the American occupation of Mexico City, the Mexican government accepted a treaty that transferred California and New Mexico to the United States.
America got a precedent, a de facto amendment to the Constitution. For another hundred years, American presidents would still defer to Congress in formal declarations of war. But during that time they would demonstrate that they had learned the Polk lesson that a determined president can force a war declaration by putting Americans in harm’s way and getting them killed. William McKinley sent a battleship to Havana amid tension with Spain in 1898, and when the ship exploded, Congress declared war on Spain. Woodrow Wilson sent American ships into the path of German submarines in 1917, and when the ships were sunk, Congress declared war. Franklin Roosevelt waged economic war against Japan in 1941, and when the Japanese responded by attacking Pearl Harbor, Congress declared war.
After that, presidents dispensed with the formality of war declarations. America fought wars in Korea, Vietnam, the Persian Gulf, Afghanistan, Iraq and Iran without congressional declarations.
The salient parts of the Constitution were never actually touched, but starting with Polk the war power effectively migrated from Article I to Article II.
Published on May 12: American Patriarch: The Life of George Washington