SMARDAN, Romania — NATO members continued their largest combat exercises of 2025 on Wednesday, testing their ability to rapidly deploy large-scale forces on the 32-nation alliance’s eastern border as worries grow over its most powerful member, the United States.

The drills in Romania, which borders Ukraine, come as a shaken Europe grapples with a new U.S. course under President Donald Trump. Defense Secretary Pete Hegseth has demanded that allies dramatically ramp up military spending and said U.S. security priorities lie elsewhere — casting doubts on Washington’s longstanding security guarantees provided to Europe.

Steadfast Dart 2025: A Show of Force

Days before the third anniversary of Russia’s full-scale invasion of Ukraine, the Steadfast Dart 2025 drills comprise about 10,000 military personnel from nine nations as part of NATO’s new Allied Reaction Force. They are taking place over six weeks in Romania, Bulgaria and Greece.

Although the Trump administration has not announced plans to pull U.S. forces from the region, Hegseth’s remark that “European allies must lead from the front” left NATO partners contemplating a potential new reality in which the U.S. is no longer the powerful, nuclear-armed backstop for the continent’s security.

Radu Tudor, a defense analyst in Bucharest, said a U.S. rollback of its military presence in Romania would be “a gift” to Russian President Vladimir Putin.

“The whole eastern flank of NATO (would) become weaker in front of Russia’s aggressive behavior,” he said, adding that it would push Romania to ask NATO allies to contribute troops and weapons to plug the gap left by several thousand American troops.

Related Story: US Defense Chief Hegseth Calls NATO Membership for Ukraine Unrealistic

NATO’s Transformation in Response to Threats

Adm. Stuart B. Munsch, commander of the Allied Joint Force Command, said threats to NATO “have become increasingly complex and unpredictable” over the past decade.

“To address this complex security environment, NATO has undergone a significant war-fighting transformation. We have taken our defensive plans from concept to reality,” Munsch told reporters at the training base on Wednesday. “This exercise … represents the culmination of our efforts and the beginning of our new force that will defend every inch of alliance territory.”

European allies have also expressed concern over being sidelined from talks between Washington and Moscow’s top diplomats on Tuesday in Saudi Arabia on working towards ending the war in Ukraine.

The fast-moving developments prompted France’s president to convene select EU countries and the U.K. for talks this week in Paris.

Strengthening NATO’s Eastern Flank

Wednesday’s combat exercises in Romania saw live-fire training and trench warfare drills. Greek and Spanish marines led exercises last week in Greece, including a mock amphibious assault.

NATO’s new Allied Reaction Force, established last July, is designed to deploy at scale within 10 days and combines conventional forces with cyber and space-based technologies. Britain leads the operation with 2,600 military personnel and 730 vehicles.

The drills also include Romania, Bulgaria, France, Greece, Italy, Slovenia, Spain and Turkey and involve 1,500 military vehicles, more than 20 aircraft and more than a dozen naval assets.

After Russia launched its full-scale invasion of Ukraine on Feb. 24, 2022, NATO bolstered its presence on Europe’s eastern flank by sending additional multinational battlegroups to Romania, Hungary, Bulgaria and Slovakia.

Since then, Romania has played an increasingly prominent role in the alliance. It has donated a Patriot missile system to Ukraine and opened an international training hub for F-16 jet pilots from allied countries, including Ukraine.

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McGrath reported from Sighisoara, Romania.