How Congress Set the Stage for Trump’s Illegal War in Iran

Much of the focus of Congress’s war powers today is on the specific power to declare war itself. This is a vital and important check, but it is not the only one. Until the twentieth century, presidents needed Congress’s approval to wage war—both to declare it as a matter of legality and to fund it as a matter of practicality. A president could not truly wage war without Congress until the mid-twentieth century because they had no real forces at their command. Funding, not authorization, is the real source of Congress’s power over the military.

“The legislature of the United States will be OBLIGED, by this provision, once at least in every two years, to deliberate upon the propriety of keeping a military force on foot; to come to a new resolution on the point; and to declare their sense of the matter, by a formal vote in the face of their constituents,” Hamilton wrote in The Federalist, Number 26. “They are not AT LIBERTY to vest in the executive department permanent funds for the support of an army, if they were even incautious enough to be willing to repose in it so improper a confidence.”

Though Hamilton does not say it outright, the two-year spending limit is a subtle but clever bit of constitutional design. Even if Congress decides to fund a war, it cannot do so beyond the next election in the House of Representatives, which also takes place every two years. This too has its roots in English history. As I’ve noted before, Congress’s general power of the purse grew out of the long history of taxation squabbles between the English monarchy, which often sought to wage war, and Parliament, representing the nobles and gentry who could obtain greater freedoms in exchange for funding it.