Expect NATO to keep raiding its arsenal to supply Ukraine with arms as a new Russian offensive is underway, but with the fight grinding into its second year — and without a formal declaration of war aims — the question put to President George W. Bush in Iraq is haunting President Biden: Where’s the exit strategy?

“The war in Ukraine is consuming an enormous amount of munitions and depleting allied stockpiles,” NATO’s chief, Jens Stoltenberg, said on Monday. “The current rate of Ukraine’s ammunition expenditure is many times higher than our current rate of production. This puts our defense industries under strain.”

While much is said about bleeding Moscow’s war machine dry, America’s allies are also hemorrhaging. “If Europe were to fight Russia,” an unnamed diplomat told Reuters on Monday, “some countries would run out of ammunition in days.”

As the American economist, Herbert Stein, said, “If something cannot go on forever, it will stop,” and signs of strain are already appearing. A year ago, Mr. Biden pledged to support Ukraine “as long as it takes,” but last week, a senior administration official told the Washington Post that they’d sent Kiev the message that America “can’t do anything and everything forever.”

It’s a sharp departure from the blowback Speaker McCarthy faced for saying that there would be no “blank check” for Kiev from a GOP House. At the time, a blank check was the only acceptable position in Washington unless one wanted to be smeared as pro-Russia, as if Ukraine was one of the several states and we would pay any price to liberate it.

No matter how noble Ukraine’s cause, the Biden administration is coming around to the reality that no foreign nation is entitled to a free hand to drain our Treasury and arsenal. The time may be right for the Republican senator from Kentucky, Rand Paul, to reintroduce his resolution — rejected last year — requiring oversight of how aid to Ukraine is spent.

In 2005, NBC News ran a story headlined, “Democrats Challenge Bush To Lay Out Iraq Exit Strategy,” which quoted the Senate Democratic leader, Harry Reid. “Most of all,” he said, “we need an exit strategy so that we know what victory is and how we can get there, so that we know what we need to do and so that we know when the job is done.”

The time to plan the end is in the beginning, but America has not bothered with a formal declaration of war since 1942. Instead, Congress has passed open-ended commitments like the use of force resolution after 9/11, which authorized the president “to use all necessary and appropriate force … to prevent any future acts of international terrorism against the United States…”

This language empowered Mr. Bush and his successors to unleash the military anywhere on the globe without having to go through the legislature. The military actions in Korea, Vietnam, Iraq, Somalia, and Afghanistan all demonstrated the danger of Congress abdicating its power to outline, debate, and declare war aims before shots are fired.

The resolution after Japan attacked Pearl Harbor was specific. It stated that “to bring the conflict to a successful termination, all the resources of the country are hereby pledged by the Congress of the United States.” Mr. Biden has made a similar commitment to Ukraine in spirit, but without tough deliberations on questions such as, “How much is this going to cost?”

Congress will not declare war on Russia, but it has a duty to spell out where our support ends and what victory Mr. Biden is empowered to deliver as commander-in-chief. A free Ukraine is in our interests, but not if it leaves America’s big stick whittled down to a toothpick, emboldening Russia to attack a NATO ally and Communist China to leap across the Taiwan Strait.

The Ukraine War and America’s commitment to it cannot go on forever, and neither can Washington’s habit of plunging into fights without respecting the intent of the Constitution to ensure that there’s an endgame in mind from day one, so we’re not left groping in the dark for an exit we can’t find.