Skip to main content

Twenty years after: assessing the consequences of enlargement for the NATO military alliance


How has enlargement affected NATO as a military organization? This article explores the strategic and military consequences of expansion for NATO as a regional defense alliance. The article makes the case that by pursuing enlargement alongside internal adaptation efforts and by failing to reconcile the tensions resulting from expanding commitments while simultaneously drawing down military forces and shuttering commands, Western leaders’ choices in the 1990s set the stage for many of the strategic problems NATO faces today.

This is a preview of subscription content, access via your institution.


  1. Within NATO the term ‘internal and external adaptation’ was adopted to describe the alliance’s ambitious post-Cold War transformation agenda. Internal adaptation referred to efforts to streamline NATO political and military structures, whereas external adaptation dealt with the adoption of new security functions like crisis management and peacekeeping (Smith and Latawski 2003).

  2. The 1991 Strategic Concept was the first strategic review to be non-classified and the fifth overall since the alliance’s creation. The alliance released an updated version in 1999. The most recent NATO Strategic Concept was released in 2010 (NATO 2018c; Naumann 1997, 7–11).

  3. This was an across-the-board average. In the Central Region, NATO’s peacetime force level was reduced by 45% (de Wijk 1997, 44; Johnston 2017, 148).

  4. Eventually, the two became linked as NATO decided to use these missions as a way to help integrate new members (Hunter 2019, 304).

  5. The levels of command were also assigned new names: Major NATO Commands (e.g., ACE and ACCLANT) became Strategic Commands (SCs); Major Subordinate Commands were renamed Regional Commands (RC); and the Principal Subordinate Commands were renamed Sub-Regional Commands (SRCs) (Pedlow n.d., 12; Young 1997b, 2; Johnson 1997, 10).

  6. Prior to the 1999 enlargement round, cost shares for the NSIP budget were last revisited in 1994; the civil budget and the military budget formulas were last reviewed in 1955 and 1966, respectively. See Government Accountability Office 1998, 2).

  7. The total cost for the second round was estimated at about $3 billion but the newly admitted members were expected to contribute approximately $300 million, resulting in a $2.7 billion price tag. See Congressional Budget Office (2000, 3) and Eck (1998, 6).


  • Adamowski, J., and Banks M. 2019. Without a NATO-Wide Effort, the Skies Along the Northeastern Flank Could Be in Peril. Defense News.

  • Allison, G. 2019. ‘Italian Jets Deploy on NATO Air Policing Mission over Romania’. UK Defence Journal.

  • Asmus, R., et al. 1995. NATO Expansion: The Next Step. Survival 37 (1): 7–30.

    Google Scholar 

  • BASIC. 1992. Military Guidance for the Implementation of the Alliance’s Strategic Concept’ BASIC. Reports on European Arms Control No. 20. London: BASIC.

    Google Scholar 

  • Berger, J. 1998. The Multinational Corps Northeast: A Meaningful and Effective Contribution by the German Army to the Goals of NATO Enlargement. Carlisle, PA: Strategic Studies Institute, US Army War College.

    Google Scholar 

  • Borawski, J. 1997. ‘NATO Restructuring and Enlargement: The Dual Challenge’. In: Young 1997a, pp. 205–216.

  • Central Intelligence Agency (CIA), 2020. The World Factbook,

  • Clemmesen, M. 1997. ‘Present and Future Command Structure: A Danish View’. In: Young 1997a, pp. 189–203.

  • Congressional Budget Office. 2003. Cost Implications of Implementing the March 26, 2003, NATO Accession Protocols. Washington, DC: Congressional Budget Office.

    Google Scholar 

  • Congressional Budget Office. 2000. Integrating New Allies into NATO. Washington, DC: Congressional Budget Office.

    Google Scholar 

  • d’Aboville, B. 2019. Beyond NATO Enlargement to Poland, the Czech Republic, and Hungary: A French Reappraisal. Hamilton and Spohr 2019, pp. 519–547.

  • Deni, J. 2004. The NATO Rapid Deployment Corps: Alliance Doctrine and Force Structure. Contemporary Security Policy 25 (3): 498–523.

    Article  Google Scholar 

  • de Wijk, R. 1997. NATO on the Brink of the New Millennium. London: Brassey’s.

    Google Scholar 

  • Eck, C. 1998. ‘NATO Expansion: Cost Issues’. Washington, DC: Congressional Research Service, updated 26 February 1998.

  • Faith, A.J. 1999. A New Military Command Structure for NATO: But at What Expense? Defense and Security Analysis 15 (3): 273–291.

    Article  Google Scholar 

  • Government Accountability Office, 1998. NATO: History of Common Budget Cost Shares. GAO/NSIAD-98-172. Washington, DC: Government Accountability Office.

  • Hamilton, D.S. 2019a. New Members, New Missions: NATO and Euro-Atlantic Architecture in the Second Clinton Administration. Hamilton and Spohr 2019: 339–384.

    Google Scholar 

  • Hamilton, D.S. 2019b. Piece of the Puzzle: NATO and Euro-Atlantic Architecture after the Cold War. Hamilton and Spohr 2019: 3–57.

    Google Scholar 

  • Hamilton, D.S., and Spohr, K., eds. 2019. Open Door: NATO and Euro-Atlantic Security after the Cold War. Washington, DC: Foreign Policy Institute/Henry Kissinger Center for Global Affairs, School of Advanced International Studies, Johns Hopkins University.

  • Hunter, R. ‘Toward NATO Enlargement: The Role of USNATO’. Hamilton and Spohr 2019, pp. 297–338.

  • Johnson, W. 1997. ‘Reorganizing NATO Command and Control Structures: More Work in the Augean Stables?’. In: Young 1997a, pp. 9–28.

  • Johnson, W., and T.D. Young. 1993. Preparing for the NATO Summit: What are the Pivotal Issues?. Carlisle, PA: Strategic Studies Institute, US Army War College.

    Google Scholar 

  • Johnston, S. 2017. How NATO Adapts: Strategy and Organization in the Atlantic Alliance Since 1950. Baltimore, MD: Johns Hopkins University Press.

    Google Scholar 

  • Joyce, M. 2005. ‘Reforming NATO Force Generation: Progress, Problems and Outstanding Challenges’. London: Royal United Services Institute (RUSI).

  • Kay, S. 2001. ‘NATO Enlargement: Who Gains? Who Loses?’. In: Schmidt 2001, vol. 1, pp. 221–234.

    Chapter  Google Scholar 

  • Lange, H., et al. 2019. To the Seas Again: Maritime Defence and Deterrence in the Baltic Region. Tallinn: International Centre for Defence and Security.

    Google Scholar 

  • Latvian Public Broadcasting, 2014. ‘€3 m Price-Tag on 2015 Baltic Air Police Mission’. 16 September 2014.

  • Lesser, I. 2000. ‘NATO Looks South: New Challenges and New Strategies in the Mediterranean’. MR-1126-AF. Santa Monica, CA: RAND Corporation.

  • Lugar, R. 1993. ‘NATO: Out of Area or Out of Business; A Call for U.S. Leadership to Revive and Redefine the Alliance’. Richard G. Lugar Senatorial Papers, Indiana University Libraries, Bloomington,, accessed 25 September 2019.

  • Martyn-Hemphill, R. 2015. ‘NATO Scales Back Baltic Air Policing’. Baltic Times.

  • Moller, S. 2019. ‘Building the Airplane while Flying: Adapting NATO’s Force Structure in an Era of Uncertainty’. Policy Brief no. 11. Rome: NATO Defense College.

  • Naumann, K. 1997. The Reshaping of NATO from a Military Perspective. RUSI Journal 142 (3): 7–11.

    Article  Google Scholar 

  • NATO, 2018a. ‘Air Policing: Securing NATO Airspace’. Last modified 16 May 2018,

  • NATO, 2010a. ‘The Alliance’s New Strategic Concept’. Last modified 26 August 2010,

  • NATO, n.d.1. ‘Allied Maritime Command’.

  • NATO, 2010b. ‘Declaration on a Transformed North Atlantic Alliance’. Last modified 12 July 2010,

  • NATO, n.d.2. ‘Exercises and Training’.

  • NATO, 2016/2017. ‘Headquarters: Multinational Division Southeast’.

  • NATO, n.d.3. ‘History—Multinational Corps Northeast’.

  • NATO, n.d.4. ‘Multinational Corps Northeast’.

  • NATO, n.d.5. ‘NATO Assurance Measures’.

  • NATO, 2018b. ‘NATO Starts Montenegro Air Patrols’. 5 June 2018,

  • NATO, 2011. ‘NATO’s Assessment of a Crisis and Development of Response Strategies’. Last modified 16 June 2011,

  • NATO, 1997. ‘NATO’s Enlargement’. Last modified 4 July 1997,

  • NATO, 2016. ‘NATO’s Readiness Action Plan’. Last modified July 2016,

  • NATO, 1999. ‘Press: Development of the European Security and Defense Identity (ESDI) within NATO’.

  • NATO, 2019. ‘The Secretary General’s Annual Report 2017’. Last modified 4 March 2019,

  • NATO, 2018c. ‘Strategic Concepts’. Last modified 12 June 2018,

  • NATO, 2008. ‘Study on Enlargement’. Last modified 5 November 2008,

  • NATO officer 1, 2017. Interview with author. Szczecin.

  • NATO officer 2, 2017. Interview with author. Szczecin.

  • NATO officer 3, 2017. Interview with author. Vilnius.

  • NATO officer, 2018. Interview with author. Rome.

  • Organization for Security and Co-operation in Europe (OSCE), 1990. ‘Treaty on Conventional Forces in Europe’. 19 November 1990,

  • Pedlow, G. n.d. ‘The Evolution of NATO’s Command Structure, 1951–2009’. Mons: SHAPE.

  • Perry, W.J. 1995. ‘The Enduring, Dynamic Relationship That Is NATO’. Remarks at Wehrekunde, Munich, Germany, 5 February 1995. Washington, DC: US Department of Defense,

  • Pfeiffer, H. 2008. Defence and Force Planning in a Historical Perspective: NATO as a Case Study. Baltic Security & Defence Review 10: 103–120.

    Google Scholar 

  • Rifkind, M. ‘NATO Enlargement 20 Years On’. Hamilton and Spohr 2019, pp. 501–518.

  • Rühe, V. ‘Opening NATO’s Door’. Hamilton and Spohr 2019, pp. 217–234.

  • Ruiz-Palmer, D.A. 2016. ‘The Framework Nations’ Concept and NATO: Game-Changer for a New Strategic Era or Missed Opportunity?’. Research Paper No. 132. Rome: NATO Defense College.

  • Schake, K. 2001. ‘Adapting NATO after the Cold War’. In: Schmidt 2001, vol. 2, pp. 29–42.

    Chapter  Google Scholar 

  • Schimmelfennig, F. n.d. ‘NATO’s Enlargement to the East: An Analysis of Collective Decision-Making’. EAPC-NATO Individual Fellowships Report 1998–2000.

  • Schmidt, G. (ed.). 2001. A History of NATO—The First Fifty Years. 3 vols. London: Palgrave.

    Google Scholar 

  • Shirreff, R. 2016. War with Russia: An Urgent Warning from Senior Military Command. New York: Quercus.

    Google Scholar 

  • Simon, J. 2002. NATO Enlargement and Central Europe: A Study in Civil-Military Affairs. Honolulu: University Press of the Pacific.

    Google Scholar 

  • Simon, J. 2011. ‘NATO’s Membership Action Plan (MAP) and Prospects for the Next Round of Enlargement’. Report no. 58. Washington, DC: Woodrow Wilson Center.

  • Smith, M. 2000. NATO in the First Decade After the Cold War. New York: Springer.

    Book  Google Scholar 

  • Smith, M., and P. Latawski. 2003. Kosovo and NATO’s Post-Cold War adaptation. In The Kosovo Crisis and the Evolution of Post-Cold War European Security, ed. M. Smith and P. Latawski, 39–65. New York: Manchester University Press.

    Chapter  Google Scholar 

  • UK Ministry of Defense, 2017. Letter. 18 December 2017. REF: FOI2017/11679/79730/16/03,

  • US Department of Defense, 2018. ‘Military Construction Program FY 2019 Budget’. Washington, DC: US Department of Defense,

  • US Department of Defense. 1998. The Military Requirements and Costs of NATO Enlargement. Foreign Policy Bulletin 9 (2): 116–125.

    Google Scholar 

  • Tuschoff, C. 2014. The Impact of NATO’s Defence Planning and Force Generation on Member States. In NATO’s Post-Cold War Politics, ed. S. Mayer, 194–211. London: Palgrave Macmillan.

    Google Scholar 

  • Walker, J. ‘Enlarging NATO: The Initial Clinton Year’. Hamilton and Spohr 2019, pp. 263–276.

  • Young, T.D. (ed.). 1997a. Command in NATO after the Cold War: Alliance, National, and Multinational Considerations. Carlisle, PA: Strategic Studies Institute, US Army War College.

    Google Scholar 

  • Young, T.D. 1997b. ‘Introduction’. In: Young 1997a, pp. 1–8.

  • Young, T.D. 1997c. Multinational Land Formations and NATO: Reforming Practices and Structures. Carlisle, PA: Strategic Studies Institute, US Army War College.

    Google Scholar 

  • Young, T.D. 1998. Reforming NATO’s Military Structures: The Long Term Study and its Implications for Land Forces. Carlisle, PA: Strategic Studies Institute, US Army War College.

    Book  Google Scholar 

Download references

Author information

Authors and Affiliations


Corresponding author

Correspondence to Sara Bjerg Moller.

Ethics declarations

Conflict of interest

The author has no conflicts of interest to declare.

Additional information

Publisher's Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Moller, S.B. Twenty years after: assessing the consequences of enlargement for the NATO military alliance. Int Polit 57, 509–529 (2020).

Download citation

  • Published:

  • Issue Date:

  • DOI:


  • NATO
  • NATO enlargement
  • Alliance management
  • Military planning