Vice President JD Vance, who has been criticized for championing the U.S. war against Iran despite his history of staunchly opposing foreign interventionism, on Wednesday defended President Trump’s effort to unwind the war through negotiation.

“Today, as I sit here, there are people in this country who want you to just keep going and keep going,” Mr. Vance told a gathering of active-duty military members at Naval Air Station Oceana in Virginia Beach, excoriating those who had tried to “attack the president of the United States for using the leverage that you gave him to engage in negotiation.”

“And why do we engage in negotiation?” he added. “Because of you. It’s not out of weakness, but it’s out of strength.”

Before becoming vice president, Mr. Vance, a former Marine who deployed to Iraq as a military journalist, was a fierce opponent of the United States’ “forever wars” who criticized the country’s leaders for embroiling the military in long overseas conflicts with shifting objectives. As vice president, he has struggled to reconcile that stance with Mr. Trump’s increasingly interventionist tendencies, particularly as he has been asked to defend the president’s decision to attack Iran to the public and at the negotiating table, where talks have failed to yield a final peace deal thus far.

The Trump administration has been roundly criticized by Democrats for launching strikes against Iran that quickly escalated into a war. The president’s approach has also been scorned by hawkish Republicans, who have complained that the emerging terms of the peace deal have been too lenient on Iran, and that they do not do enough to preclude Iran from developing nuclear weapons.

Mr. Vance has offered various rationales to explain his defense of the Iran war, which he argues is not an ideological shift. He has said that he always believed Iran should not have a nuclear weapon. He has argued that the Trump administration pursued and achieved “clear objectives” in Iran, a talking point he repeated on Wednesday. Those objectives include dismantling Iran’s nuclear program, crippling the military and destroying the defense industrial base — though U.S. intelligence suggests that Iran’s military was not nearly as affected as the administration has portrayed.

On Wednesday, Mr. Vance drew on his experience in Iraq to support his contention that Mr. Trump was using the military to help him negotiate a durable peace in Iran.

“There were people who learned the lesson that we could never use the military again, but that’s not the right lesson,” he said.

“There were also people who learned a different lesson, an equally wrong lesson, that the solution to the problems that we had in the early 2000s was to ask you to do more and more and more and more without giving you a clearly defined objective,” he added.

But while Mr. Vance cheered the military for carrying out Mr. Trump’s orders to attack military and nuclear interests in Iran, he did not offer any timeline for a final cessation of hostilities — and with it, the end of deployments.

Instead, the vice president appeared to acknowledge that Mr. Trump had asked more of the military than his predecessors, whom Mr. Vance built his political career on criticizing.

“You guys have done more in the last 18 months. The president of the United States has asked you to do more than I think any group of service members has ever been asked to do,” Mr. Vance said. “And yet you’ve done it.”