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Evaluating NATO enlargement: scholarly debates, policy implications, and roads not taken


NATO’s enlargement into Central and Eastern Europe after the Cold War is the subject of significant debate in academic and policy circles. With few exceptions, however, this debate focuses on single issues, such as whether enlargement led to the decline of the West’s relations with Russia. In this framing document, we look to expand the debate. We do so by sequentially reviewing the process by which NATO enlarged, outlining the array of issue areas within which to assess the consequences of NATO enlargement, and highlighting the particular importance of counterfactual analysis to any judgment of enlargement’s legacy. Building on a May 2019 workshop at Boston University, we also summarize the results of several articles that collectively evaluate the consequence of expansion for the USA, Russia, non-US NATO members, and the organization itself. Finally, we conclude by outlining elements of a broader research program on the aftereffects of NATO enlargement.

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  1. In the original logic for Partnership for Peace, the program would offer Eastern European states (and Russia) institutional ties to NATO but stop short of full membership. This approach was favored by the Pentagon as well as officials at the State Department who worked on Russian policy.

  2. The 1949 Washington Treaty establishing NATO provided that the alliance was open for invitation to ‘any other European State in a position to further the principles of this Treaty and to contribute to the security of the North Atlantic area.’ See NATO (1949).

  3. Clearly, not all of these assumptions are in harmony—the logic faced a number of internal tensions.

  4. Illustrating the point, testimony by Defense Department officials at the time of NATO enlargement focused primarily on the budgetary implications of NATO enlargement rather than the tasks of defending new NATO member states; see U.S. Senate, Committee on Foreign Relations 1998, 131–152. For subsequent military difficulties, see Sara Moller’s and Paul Van Hooft’s articles in this issue.

  5. An example illustrates the point. As the historian John Lewis Gaddis noted in Strategies of Containment, a major difficulty confronting the US’ initial approach to containment was the inability of George Kennan—its principal architect—to clarify the strategy’s objectives for those charged with implementing the policy; see Gaddis (1982, 53–86).

  6. That said, they may be fostering deeper institutional integration; see Zielinski and Schilde (forthcoming).

  7. In Fearon’s terms, we are interested not only in whether Cause C is linked to Outcome E, but in further identifying what outcomes instead of E would have obtained if C were absent.


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The authors thank Michael Desch as well as the authors of this special issue for comments at an earlier conference hosted by Boston University that was funded partly by the Charles Koch Foundation. Thanks also go to Agneska Bloch and Stephen Dyer for their research assistance, and to Monica Achen for copyediting all pieces in this special issue.

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Correspondence to Joshua R. Itzkowitz Shifrinson.

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Goldgeier, J., Itzkowitz Shifrinson, J.R. Evaluating NATO enlargement: scholarly debates, policy implications, and roads not taken. Int Polit 57, 291–321 (2020).

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  • NATO
  • Russia
  • USA
  • Europe
  • International security
  • Counterfactuals