Observers of President Barack Obama’s rhetoric against Russia this week may have heard undertones of a pivot back to Europe. But despite aggression from President Vladimir Putin and pressure from some NATO partners and U.S. politicians to intervene, Obama is staying the course: reassuring allies of American commitment while pushing them to do more, and a more agile, efficient use of the U.S. military in the region.

A nuanced foreign policy approach is typically a tough sell, and it’s all the more difficult in the current political climate. Obama faces a war-weary American public and a Congress both concerned about projections of weakness and tightening defense budgets that ballooned after more than a decade of ground wars in Iraq and Afghanistan.

“If, in such a moment, you ever ask again ‘Who will come to help?’ you’ll know the answer—the NATO Alliance, including the armed forces of the United States of America…You lost your independence once before. With NATO, you will never lose it again,” Obama told European allies Wednesday in a speech in Estonia ahead of last week’s NATO summit in Wales.

While Obama used the NATO summit to reassure Eastern European allies he is prepared to counter Russian aggression, he also made sure not to lure them into a false sense of security that the U.S. is going to do it for them.

“Even as we keep our countries strong at home, we need to keep our alliance strong for the future…So this week’s summit is the moment for every NATO nation to step up and commit to meeting its responsibilities to our alliance.”

It’s a familiar message. Before sending hundreds of ground troops into Iraq to protect U.S. interests and help the Iraqi Army defeat the Islamic State, Obama made clear to the government of Iraq that the U.S. can’t fight this fight for them.

On Friday, Obama announced that all 28 NATO nations have agreed to contribute “for as long as necessary” to a mix of new and renewed initiatives, such as a readiness action plan to increase the alliance’s presence in Eastern Europe and develop a rapid response force, as well as more security assistance to Ukraine.

“This commitment makes clear that NATO will not be complacent,” Obama said. “Our alliance will reverse the decline in defense spending and rise to meet the challenges that we face in the 21st century.”

The U.S. shoulders 73 percent of the aggregate military spending of all NATO members, up from 68 percent in 2007, according to NATO. Obama made note of the $1 billion European Reassurance Initiative he announced in Warsaw in June. And the U.S. has already increased rotations of personnel in the Baltics, involvement in air policing, military-to-military exercises and naval patrols in the Black Sea.

“An increased presence serves as the most effective deterrent to any additional Russian aggression that we might see,” Obama said Friday.

But the U.S. has been downsizing its footprint in Europe for more than a decade now. The Pentagon has cut its infrastructure there by 30 percent since 2000.

In January of last year, the Pentagon released its blueprint to reduce its budget over the next decade by $487 billion, in part by shrinking the U.S. military’s presence in Europe, withdrawing several combat brigades and closing an Army Corps headquarters. Then March 1, 2013 triggered the across-the-board sequester cuts, forcing the Pentagon to quickly find billions in cost reductions, such as grounding fighter squadrons in Europe. The belt-tightening has continued, with the Pentagon announcing in May that it would close 21 facilities it determined were outdated, saving some $60 million a year. USAF Lt. Col. David Westover, a EUCOM spokesman, said seven have been closed thus far and the other closures are underway.

More rounds of closures are planned as part of the European Infrastructure Consolidation review, which began before Russia’s intervention in Ukraine. It is now complete, according to Pentagon spokeswoman Lt. Col. Vanessa Hillman. “A careful and deliberative set of recommendations” should be on Defense Secretary Chuck Hagel’s desk in the coming weeks, she said. Pentagon spokesman Lt. Col. Steve Warren told Defense One that despite recent events in Europe, current and completed consolidations and closures are not currently being reconsidered.

(Read More: Obama Outlines Expanded Troop Plan for the Baltics)

In the wake of Russia’s annexation of Crimea earlier this year and its continued aggression against Ukraine, a handful of key voices on national security have warned that now is not the time to keep scaling back the U.S. military presence in Europe.

Chairman of the Joint Chiefs of Staff Gen. Martin Dempsey says while the military must become more efficient, it cannot pare back much further if it wants to maintain its deterrent capability.

“My instinct is that you won’t see return of forces to Europe on a permanent basis, but that you will see, I hope what you will see is a recognition that we’ve been a little complacent about Europe for probably the last 10 or 15 years,” Dempsey said at the Aspen Security Forum in July. “And we can no longer afford to be complacent about Europe. And we need to increase the tempo, the quality of the training and the readiness that we provide to our European allies.”

On Capitol Hill, members of Congress are warning not to neglect security in Europe, even as numerous threats around the globe, including the pivot to Asia, demand attention.

“I have consistently pushed the Pentagon to save money and streamline operations, but Russia's invasion of Ukraine has underscored the fact that it is unwise to take security in Europe for granted,” Sen. Kelly Ayotte, R-N.H., told Defense One on Friday.

Ayotte and others have also questioned the Defense Secretary’s authority to close European bases without the approval of Congress. “I will press the Pentagon to explain its plans going forward for U.S. force posture in Europe—which should be based on an objective and current analysis of the military posture required to protect U.S. national security interests, not outdated and budget-driven plans developed before Moscow’s invasion of Ukraine began,” Ayotte said.

Sen. Jim Inhofe, R-Okla., ranking member of the Armed Services Committee, also expressed concern that defense budget plans for Europe must adapt to new realities.

“Russia’s increasingly belligerent behavior, including its invasion of Ukraine, has shown that the hopes for a peaceful post-Cold War period have proved short lived,” Inhofe said. “The rising instability across the Middle East and North Africa and a lack of persistent basing there has placed an even greater demand on our personnel and basing in Europe.”

Inhofe cited congressional testimony from AFRICOM Commander Army Gen. David Rodriguez and CENTCOM Commander Army Gen. Lloyd Austin that basing troops and equipment in Europe is “critical” to the mission.

"It makes sense and I support examining ways to increase efficiencies in our basing in Europe, but that should not mean reducing forces or force structure,” Inhofe said. “At a minimum, force structure in Europe should hold steady and serious consideration should be given to increasing it given the rise in threats and the critical role our European basing plays in enabling strategic access to Europe and supporting operations in Africa and the Middle East."

Today, even a lighter U.S. footprint in Europe includes 29 main operating bases or forward operating sites in 12 countries, hosting roughly 69,000 troops, according to Westover. About 40,000 are based in Germany, 11,000 in Italy and about 9,500 in the United Kingdom.

Ten years ago, the U.S. military presence in Europe included about 100,000 troops and more than 500 U.S.-controlled sites, which could range in size from a radar antenna site to a large base, such as Ramstein Air Base, in Germany.

(Read More: Pentagon's Reliance on Europe is 'Wishful Thinking')

But fewer facilities hasn’t degraded the ability of the U.S. military and its allies to operate in Europe. For example, in 2008, the U.S. did 117 joint or multi-national exercises with NATO in Europe. There have been 139 exercises so far in 2014. A defense official said the shift has offered an opportunity for NATO partners to improve their own capacity. As a result of fighting shoulder-to-shoulder with U.S. troops for the past 13 years of war in Afghanistan and Iraq, NATO forces may even be more “combat-ready” than ever to go up against Russia and its pro-separatist allies, the official said.

When Congress returns from recess next week, there is a chance, given the spate of new threats, in particular from the Islamic State, it may try and grant the Defense Department some relief on sequestration. “Congress and the president also must act now to address defense sequestration, which is damaging our military readiness at a time when we face increasing threats,” Ayotte said.

But what is more likely is Congress granting some portion of Obama’s $65.8 billion Overseas Contingency Operations request, which is not tied to the overall defense budget. The OCO includes the $1 billion European Reassurance Initiative.

Still, as Obama said Friday of the threats to European security: “It is a time of transition and a time of testing.” That is also true for his leadership.