Mr. Trump shares some of these inclinations. “Great nations do not fight endless wars,” he proclaimed in the State of the Union. He has pledged to pull most ground troops out of Syria and is pursuing negotiations with the Taliban in Afghanistan. On the whole, though, most advocates of restraint find little to like in Mr. Trump’s militarized foreign policy. They see a president who has attempted to assert American dominance over the world, boosting the defense budget, escalating military interventions in the Middle East and Africa, and imposing new sanctions on Iran and now Venezuela.

Yet they also see an opportunity to constrain the United States’ military adventurism by opposing the war powers of an unprincipled and unstrategic commander in chief. On Feb. 13, antiwar forces scored a victory when the House voted to end military support for Saudi Arabia’s war in Yemen. If the resolution passes the Senate, it will mark the first time Congress has invoked the 1973 War Powers Act in order to bind the president to remove American forces active in hostilities abroad.

The bill also offers a template for further withdrawals, according to its Senate sponsors, Democrat Chris Murphy, Independent Bernie Sanders and Republican Mike Lee. “Since 9/11, politicians have become far too comfortable with American military interventions all over the world,” they have written. The next step may be to repeal the Authorization for the Use of Military Force passed after the Sept. 11 attacks, which successive presidents have used to justify almost unlimited warmaking in the greater Middle East.

Restraint is advancing on the left of the Democratic Party, but it’s not yet clear whether it can pierce the center as domestic proposals like Medicare for All have done. Calls to cut military spending, advanced by Mr. Sanders and House progressives, have not quite become a core principle of the progressive movement. And advocates of restraint tend to become less vocal and unified when they turn beyond the Middle East. The sponsor of the House’s Yemen resolution, Representative Ro Khanna, has distinguished himself by supporting diplomacy with North Korea and opposing regime change in Venezuela, but he stands apart. The restraint coalition would benefit from taking a similarly global view if it is to advance a comprehensive alternative to the status quo.

The Coming Clash?

Does the future belong to great power competition or restraint? Partisans of each camp have good reason to feel the wind at their back. Decades of policy failure have converged with the daily eruptions of President Trump to throw open the question of what America’s place in the world should be.

What’s more, the two camps have not quite trained their sights on each other. That is partly because advocates of great power competition in the establishment remain obsessed with Mr. Trump, while advocates of restraint have been marginalized for so long that they need to pick their battles. One can even glimpse the outlines of a tacit bargain between them, breaking down geographically: As restrainers try to end wars in the Middle East, centrists pivot toward the Pacific, where the adversaries are larger but war less likely.

For now, savvy politicians can adopt both positions at once. Ms. Warren, for example, denounces Chinese and Russian behavior at the same time that she promises to remove troops from Afghanistan and “cut our bloated defense budget.” And Democrat-leaning experts not previously outraged by America’s Middle East entanglements now bemoan them as distractions. Before long, it will be only anti-Iran, pro-Israel hard-liners — members of the Trump administration and Democratic leadership included — who will strongly defend America’s posture in the region.