Trump just raised the $39 trillion national debt with the largest budget hike since World War II—and nobody can figure out how to pay for it

President Trump’s fiscal year 2027 budget proposal, released Friday, calls for boosting total defense funding to $1.5 trillion—a jump that most economists say would represent one of the largest budget increases in American history, rivaling the wartime mobilization of World War II.

The proposal would increase base defense discretionary spending by $251 billion and funnel an additional $350 billion into defense through a new reconciliation bill, while cutting nondefense discretionary spending by just $73 billion—a 10% reduction that budget watchdogs say falls far short of offsetting the military buildup. The net result, according to the nonpartisan Committee for a Responsible Federal Budget (CRFB), is a defense expansion of more than $3.2 trillion over the next decade, adding fuel to a national debt already hovering around $39 trillion.

“The gap between rhetoric and reality is just so massive,” said Steve Hanke, professor of applied economics at Johns Hopkins University. “MAGA was told an untruth by Trump—no foreign wars, no adventurism. Now the defense budget has come in at $1 trillion, and he wants $1.5 trillion. This is a massive militarization—completely the opposite of what he told his base.”

Kent Smetters, faculty director of the Penn Wharton Budget Model, said this isn’t quite the largest budget increase in U.S. history—just the largest in the past 80 years or so. The U.S. military budget request of $100 billion in 1943—the peak of World War II mobilization—is worth approximately $1.9 trillion in today’s dollars, by Smetters’s calculation and even more as a share of GDP. “The movement of $350 billion toward mandatory spending is pretty interesting,” Smetters added, flagging how the reconciliation maneuver structurally shifts the nature of the defense commitment in ways that make it harder to reverse.

The budget arrives without official top-line deficit or debt figures, which CRFB president Maya MacGuineas described as an “astonishing lack of information.” The White House’s supplemental documents project that debt would fall to roughly 94% of GDP by 2036, compared with 120% in the Congressional Budget Office’s baseline—but only by assuming 3% average annual real GDP growth over the entire decade. Smetters flagged that assumption as “quite high” and a subject warranting its own scrutiny.

More than a month into the U.S. military campaign against Iran, President Trump finds himself in a precarious political moment, presiding over a deeply unpopular war with widespread economic fallout and facing some of the lowest approval ratings of his second term. The costs have been staggering: The war cost an estimated $11.3 billion in its first six days alone, and new estimates put total spending at roughly $30 billion to $45 billion just over a month in. Meanwhile, the administration has not articulated a clear endgame, with stated reasons for the attack shifting repeatedly—from dismantling Iran’s nuclear program, to regime change, and back again.

Gas prices have surged by roughly a third; the stock market has tumbled to its lowest levels of the year, before recovering on the faint hope of the war ending soon; and even Trump’s own base is showing signs of erosion, with approval among his 2024 voters down six points and support among independents plunging to 22%. At a private White House event on Friday, Trump uttered the unthinkable, according to the Associated Press, saying that America’s century-old social safety net might be demolished to pay for military adventurism. “We’re fighting wars. We can’t take care of day care,” Trump said. “It’s not possible for us to take care of day care, Medicaid, Medicare—all these individual things. They can do it on a state basis. You can’t do it on a federal.”

‘Plowshares into swords’

Hanke reached for a biblical image to capture the scale of the reversal. “It’s a classic plowshares into swords,” he said—invoking Joel 3:10’s call to remilitarize, the deliberate inversion of the prophet Isaiah’s famous vision of lasting peace. The phrase has entered secular use to describe exactly this kind of moment: the urgent conversion of a peacetime economy back onto a war footing. Given Europe’s parallel rearmament surge, it is a shorthand with renewed global resonance.

“With deficits larger than 6% of GDP and debt around the size of the economy, the president doesn’t propose any plan for putting our budget on a sustainable path,” MacGuineas said.

Another nonpartisan watchdog, Taxpayers for Common Sense, noted that since President Trump took office in 2025, the national debt has increased by $2.8 trillion, and taxpayers are now paying nearly $1 trillion annually just to service that debt. “This budget request does nothing to improve the nation’s fiscal trajectory,” the group said. “In fact, it moves us further in the wrong direction.”

The budget will set the U.S. on a “perilous fiscal path,” the group argued, calling the $1.5 trillion Pentagon spending spree “a major driver of this dangerous fiscal trajectory.” With the administration seeking much of the funding boost through the reconciliation process, the group argues that it amounts to “handing the Pentagon an unaccountable slush fund.”

Federal Reserve Chair Jerome Powell has already issued a public warning about the trajectory. “The country has to get back to ensuring that the economy is growing fast enough to keep pace with spending,” Powell said earlier this week in a moderated conversation at Harvard University. “It will not end well if we don’t do something fairly soon,” he said, referring to the growth rate of the nation’s $39 trillion debt and annual deficits.

The budget also leaves Social Security on track toward insolvency within the decade, according to CRFB, without proposing structural fixes. Hanke noted the cascading pressure the defense surge creates. “Once you push defense to $1.5 trillion, that puts Social Security on even shakier ground,” he said. In the biblical sequence Hanke invoked, the plowshares-into-swords moment is the penultimate act—the mobilization before the reckoning. For America’s fiscal hawks, the reckoning feels closer than ever.

For this story, Fortune journalists used generative AI as a research tool. An editor verified the accuracy of the information before publishing.

This story was originally featured on Fortune.com