After the Ballots: What the U.S. Elections Mean for NATO

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This commentary is part of a report from the CSIS Geopolitics and Foreign Policy Department entitled The Global Impact of the 2024 U.S. Presidential Election. The report features a set of essays assessing the meaning of the election for Europe, Russia, Eurasia, the Indo-Pacific, the Americas, Africa, and the Middle East.

The U.S. relationship with NATO will likely enter a new era regardless of who enters the White House next January. Should former president Trump return to the White House, NATO will likely see a significant pullback of U.S. involvement, creating a deep crisis inside the alliance. Should Harris win, the changes will be more subtle. She will likely continue the policies of the Biden administration. But her presidency, as with President Obama’s before, would mark the beginning of a post–Cold War generational shift in U.S. leadership, likely with less attachment to NATO and Europe.

Russia’s 2022 invasion of Ukraine exposed Europe’s deep military dependence on the United States. European security is centered and organized around the United States through NATO, with European forces playing a largely supporting role to a U.S.-led effort. While individual nations contribute forces and resources to NATO, the United States ultimately provides key strategic capabilities for the continent, such as air refueling, tactical intelligence, battlefield command and control, and substantial stockpiles of ammunition—a resource lacking throughout Europe. European NATO allies have stepped up by dramatically increasing defense spending by about a third, to $380 billion per year. Yet Europe still acts not as a continent but as 30 bespoke militaries operating different kit, which makes it highly questionable whether Europe could defend itself without the United States. On top of that, increased defense spending has not focused on reducing Europe’s overall dependence on the United States by addressing Europe’s critical capability gaps and dependencies. The United States therefore remains indispensable to European security and NATO. A sudden pullback of U.S. forces from NATO would leave a gaping hole in the European security architecture that could not be easily filled. Europeans would need to procure and build major capabilities, which would take many years, and NATO and European militaries would need to change how they work together.

Under a Trump Administration

Undoubtedly, a second Trump administration would have profound implications for NATO. Trump has rhetorically attacked NATO for decades but now appears to have concrete plans to follow through on reducing U.S. involvement in the NATO alliance. A second Trump administration would be unlikely to fully withdraw from NATO, as such an action would require the approval of the Senate. Nevertheless, organizations supportive of Trump are making concrete policy proposals, such as one highly discussed proposal calling for a “dormant NATO” and the Heritage Foundation’s Project 2025 calling for “transform[ing] NATO” by shifting the conventional military burden to Europe. According to a video posted to Trump’s campaign website in March 2023, he is ready to “finish the process” that began in his first term of “reevaluating NATO’s purpose and NATO’s mission.”

While Europeans may hope that increases in defense spending will soften Trump’s hostility, they are unlikely to have much of an impact. Trump and his allies are ultimately frustrated by Europe’s military dependence on the United States, so the call for more spending is directed at reducing the United States’ role in Europe’s security, not strengthening NATO. Trump’s allies are no longer focusing on defense spending as an issue solely with NATO; many are looking at ways for European countries to assume more of the military burden. Proposed plans include the United States continuing to extend its nuclear umbrella to NATO and maintain its bases in Germany, England, and Turkey, while forcing Europe to assume responsibility for conventional forces. 

Another plan proposes a two-tier system that challenges the sacredness of Article 5 of the North Atlantic Treaty by splitting allies into two tiers: one that meets the threshold of spending at least 2 percent of national GDP on defense and another that does not. Those that fail to meet the spending target would no longer “enjoy the defense largess and security guarantee of the United States.” A second Trump administration could also look at reviewing NATO’s enlargement policy, specifically regarding Ukraine, as Trump earlier this summer noted that NATO’s promise for eventual Ukrainian membership was a “mistake,” attributing it as the cause of Russia’s 2022 invasion.

Under a Harris Administration

A Harris administration would mark a generational shift in U.S. leadership. President Biden’s outlook is very much shaped by the Cold War and carries a deep attachment to NATO and transatlantic relations. A Harris administration would likely continue Biden’s strong support for NATO and Ukraine. Yet because European security has never been more at threat since the Cold War, European allies would inevitably feel somewhat insecure with the transition from Biden to Harris.

European allies will constantly seek reassurance to an extent that Harris cannot satisfy. She will likely find it difficult to match Biden’s engagement, which has felt deeply personal and rooted in decades of engagement. While Harris lacks deep ties to Europe, her current national security team does not. Her national security adviser, Phil Gordon, is a well-respected career Europe expert, and Harris has tapped U.S. ambassador to NATO Julianne Smith for a senior State Department position. Gordon and Smith continuing to serve in a Harris administration would provide considerable continuity and reassurance to Europe.

Ultimately, U.S. commitment to NATO will remain rock solid even if U.S. attention in a Harris administration shifts elsewhere, particularly at the beginning of a presidency when there is often a focus on domestic issues. A Harris presidency might be similar to the Obama presidency, where U.S. policy remained solidly committed to NATO but, as former Italian prime minister Enrico Letta concluded, “To many Europeans, Obama is the president who didn’t love them enough.”

Policy Recommendations for the Next U.S. Administration

The United States must act with great care when it comes to the NATO alliance, as it is the most powerful and longest-lasting military alliance in history. An abrupt pullback of U.S. forces from NATO would leave European security badly exposed. Europe faces an acute threat from Russia, as well as considerable instability in its periphery. It will take many years, if not decades, for Europe to build its own “European pillar” of NATO to reduce the conventional military demands on U.S. forces. The effort to construct such a pillar should have begun after the Cold War with the formation of the European Union. But due to European differences and U.S. opposition, the effort never got off the ground.

It is time for the United States to strongly support the creation of a European pillar. For a Trump administration, there must be an understanding that this effort will take considerable time. For a Harris administration, there must be an understanding that continued U.S. opposition to a European pillar, as well as EU defense efforts, will require considerably more U.S. engagement and involvement in Europe over the longer term—something the United States will likely struggle to provide given the focus on the Indo-Pacific.

Ultimately, building a European pillar within NATO will require considerable European defense integration, in which the European Union must play a growing role. The United States’ insistence on the European Union doing more on defense—from generating a common pool of funding to harmonizing Europe’s fractured defense industrial landscape—is critical.

Max Bergmann is director of the Europe, Russia, and Eurasia Program and Stuart Center in Euro-Atlantic and Northern European Studies at the Center for Strategic and International Studies (CSIS) in Washington, D.C. Sissy Martinez is an associate fellow and associate director for the CSIS Europe, Russia, and Eurasia Program.

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Max Bergmann
Director, Europe, Russia, and Eurasia Program and Stuart Center
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Sissy Martinez

Sissy Martinez

Former Associate Fellow and Associate Director, Europe, Russia, and Eurasia Program