Blindsided by President Donald Trump’s drawdown of troops in Europe, Republican defense hawks say they’re eyeing action to push back.

Trump’s successive changes have inflamed Republicans focused on defense who argue that reducing America’s military footprint in Europe undermines NATO and signals weakness to Russian President Vladimir Putin. While the Republicans back Trump’s push for allies to share more of the burden for Europe’s security, the president’s surprise moves have provoked a potential legislative backlash.

Closed-door discussions are underway to draft provisions in the next defense spending and policy bills that would potentially withhold funding for any troop changes or direct the reversal of recent moves. Lawmakers told NOTUS they are weighing their options as they draft their next National Defense Authorization Act, a massive bill that is likely to pass by year’s end.

“That’s one option,” Sen. Mike Rounds, a senior Republican on the Senate Armed Services Committee and appropriations committees, said of the policy bill. “The other challenge to it will be through the appropriations process — as to where we appropriate the dollars, or what the penalties may be for not following through with congressional oversight.”

Republican House and Senate armed services leaders already passed provisions last year in the 2026 defense authorization law that bar a president from drawing down U.S. forces on the continent below 76,000 without coming to Congress first. There are currently between 80,000 and 85,000 U.S. service members deployed to European posts, though only 65,000 are permanently assigned there.

Lawmakers say that before the administration canceled a deployment of 4,000 troops to Eastern Europe and chose to pull 5,000 troops from Germany, they should have been told, even though troops haven’t been reduced below the threshold.

Senate Armed Services Chair Roger Wicker said he was “not at all happy about” the troop moves.

“Nor have I been called by anyone in the administration,” he said, declining to detail what recourse he might pursue through the next policy bill.

House Armed Services Chair Mike Rogers has vowed to inflict “pain” if the administration breaks the law, without specifying what measures he might take.

“We are going to mandate that the department follow the statutory minimums that are set in statute on force posture,” Rogers told Army officials at a hearing Friday. “And if there are attempted deviations, we will remedy them and impose a pain when — if — they aren’t complied with.”

Beyond possible legislative actions, at least one Republican senator said they expect colleagues to “hold” nominees to Pentagon posts who need Senate confirmation. That senator spoke on condition of anonymity to discuss a sensitive internal matter.

The new troop moves in Europe come after German Chancellor Friedrich Merz publicly questioned Trump’s strategy with the U.S.-Israeli war with Iran, and Trump harangued allies for not doing more to help in the conflict.

Vice President JD Vance defended the troop movements in a White House news conference as “promoting European independence and sovereignty.” He said European media was overreacting to a “standard delay” and not a permanent reduction in troop levels.

“Poland is capable of defending itself with a lot of help from the United States,” Vance said. “We’re not talking about pulling every single American troop out of Europe. We’re talking about shifting some resources around in a way that maximizes American security.”

NATO’s supreme allied commander said at a press conference in Brussels on Tuesday that Europe should expect more U.S. troop withdrawals over time, casting the drawdown as part of a long-term shift as European allies build more of their own conventional defenses.

U.S. Air Force Gen. Alexus Grynkewich, who leads NATO forces, said a stronger “European pillar” of NATO would allow the U.S. to reduce its presence on the continent and focus on capabilities that allies still cannot provide themselves.

Republicans are split over how far to go in pressuring NATO allies.

Sen. Eric Schmitt, a Trump ally on the Senate Armed Services Committee, said he was against the 2026 defense bill NDAA guardrails and would “vehemently oppose” any like-minded efforts in the next bill.

“The commander-in-chief has the ability to make these decisions, and a lot of my colleagues like to play president a lot,” Schmitt told NOTUS. “The time has come for us to really have a serious conversation about our European allies doing enough, and if they’re not, there certainly need to be consequences for that.”

In the meantime, Sen. Kevin Cramer, a senior Senate Armed Services Republican, said Congress should demand answers from Pentagon policy chief Elbridge Colby, seen as a leading figure behind the moves.

“Well, if we have to go stronger, we should,” Cramer said. “In the meantime, I think Elbridge Colby should get his butt over here and talk to the Armed Services Committee about it.”

Some Senate Armed Services Democrats say they expect this year’s defense bill to address the troop drawdown, though there was no specific language as of Tuesday. Lawmakers may require the administration to notify Congress ahead of a potential troop move in Europe, to allow enough time for lawmakers to block it.

“It’s happening in the defense committee now, as we are writing the bill,” Sen. Tim Kaine, a senior Democrat on the Senate Armed Services Committee, told NOTUS. “We don’t need to have a separate hearing about this. Everybody on the committee is talking about it, and there’s some significant concerns that are bipartisan in nature.”

The panel’s top Democrat, Sen. Jack Reed, said the administration must explain its strategy.

“We’re taking steps to ensure that they’re aware of the limits we’re imposing, and so it’s not like we’re just making suggestions; we’re putting laws in place,” Reed said.