The Constitution grants Congress the power to declare war. It also gives Congress the power of the purse, including power over the Pentagon’s checkbook. Now, Congress should leverage these powers to rein in an unauthorized war against Iran.
Late last month, the U.S. launched a war on Iran without congressional authorization. U.S. and Israeli strikes have reportedly killed over 1,300 Iranian civilians, including at least 175 people at a girls’ school, most of whom were students. Preliminary results of a Pentagon investigation found that the U.S. was responsible for the strike on that school. Seven U.S. servicemembers have been killed, and about 140 have been injured, in retaliatory strikes by Iran. As the human costs rise, so do the costs to taxpayers.
When the U.S. struck Iran last July, that short but extensive operation cost taxpayers over $2 billion. The current round of strikes, which the administration has said could last five weeks or longer, is costing far more. This week, the Pentagon told Congress that the first six days of the war cost over $11.3 billion. Thirteen days into the war, that figure is now out of date. With daily cost estimates ranging from $890 million to $2 billion, total costs so far could be over $26 billion. Further costs will spiral quickly, particularly if the U.S. deploys ground troops.
Shortly after the war started, President Trump said it will continue “until all of our objectives are achieved,” and that “I don’t have the yips with respect to boots on the ground — like every president says, ‘There will be no boots on the ground.’ I don’t say it.” Whether or not the administration is seriously considering ground troops is hard to say, but the refusal to rule them out is real. And the objectives seem to be constantly shifting. We’ve heard everything from eliminating Iran’s nuclear capabilities (again), to protecting American troops from retaliation for Israeli strikes, to eradicating Iran’s ballistic missiles, to demolishing their naval threat to the Strait of Hormuz, to regime change, and more.
We’ve seen this movie before. At the start of the Iraq War, we warned that costs would get out of control, and we were right. The Bush Administration said it would take a matter of days, weeks, or months, but no longer. The initial phase of the war resembled that timeline, but the nation-building and ongoing battles that followed ultimately cost taxpayers over $2 trillion, and claimed the lives of thousands of U.S. servicemembers and hundreds of thousands of Iraqis.
For all its costs in blood and treasure, at least the Iraq War was authorized by Congress. But after decades of administrations in both parties waging war with increasingly dubious legal justifications, congressional authority over the decision to go to war is on death’s door.
Last week, Congress narrowly defeated war powers resolutions that would have explicitly prohibited further military action against Iran without congressional approval. But even if the measures passed, enacting them would require a two-third majority to overturn a certain veto.
Lawmakers could continue pursuing additional war powers votes to keep lawmakers on record and pressure the administration to end the war. But rather than relying exclusively on a procedural maneuver that turns congressional war powers on their head by effectively requiring a two-third majority to reject unauthorized wars, Congress should start asserting its war authority through one of the few tools it has left—the budget.
Less than two weeks into the war, some lawmakers are already signaling support for an anticipated $50 billion supplemental spending request to help cover the costs of war. To be sure, the ongoing attacks—both on Iran and from Iran—consume a massive amount of munitions, ordnance, missiles, and defensive equipment. But the Pentagon has more than enough funding to restock those supplies. Lawmakers gave the Pentagon an 18% increase in fiscal year 2026 appropriations, including a $152 billion slush fund in the One Big Beautiful Bill Act (OBBBA). The Pentagon has plenty of flexibility to use those funds as it sees fit.
Congress should consider what’s included in a supplemental, but ultimately, any supplemental war funding should be contingent on an authorization for the use of military force. This isn’t about partisanship—it’s about constitutional duty and fiscal common sense. If Congress is not willing to vote to authorize this war, it should not vote to spend more taxpayer dollars on it.
Looking ahead, the President has said that he will request $1.5 trillion for the Pentagon’s next budget, a 42% increase on top of the 18% boost this year. To put that into perspective, on an inflation-adjusted basis the Pentagon budget grew nearly 50% since the turn of the century—this would be nearly 50% in one year.
The United States is facing $38.9 trillion in debt, and the cost of servicing that debt is $1 trillion a year and rapidly growing. Even without the huge increase in Pentagon funding the president is seeking, the nonpartisan Congressional Budget Office projected a $1.7 trillion deficit in FY27.
Beyond the existential need to start filling in the fiscal hole that policymakers are digging, the nation faces pressing domestic needs. Billion-dollar-plus disasters are getting more frequent and severe. Healthcare premiums are out of control, a problem the administration has said it wants to address. Food insecurity among children and veterans is unacceptably high, according to the Department of Veterans Affairs. These are national security issues too.
As next year’s budget takes shape, lawmakers should make a broader stand to end this unauthorized war and reclaim their authority over future decisions to go to war. In addition to rejecting supplemental war funding and another budget increase, lawmakers could include provisions in the budget to forbid the use of funds for ongoing military operations against Iran without explicit congressional approval. As another costly unauthorized war of choice unfolds before our eyes, Congress must act. The budget is the place to do so.
