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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.

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  1. 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. 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. 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. 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. 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. 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. 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).


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Correspondence to Sara Bjerg Moller.

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

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  • NATO
  • NATO enlargement
  • Alliance management
  • Military planning