On 12 March 1999, Czechia, Hungary and Poland walked into NATO as the first former Warsaw Pact members to do so. Twenty-five years later Sweden became the 32nd member. The stretch between those two dates is the story of how the Alliance grew after the Cold War, and of why Moscow never accepted it.
A study, then a first wave
The door opened slowly. In 1995 the Alliance published a study on enlargement that concluded the end of the Cold War offered a unique chance to build better security across the whole Euro-Atlantic area. Czechia, Hungary and Poland were invited to start accession talks at the Madrid Summit in 1997. NATO then launched the Membership Action Plan, or MAP, at the Washington Summit in April 1999, a programme meant to help aspiring members prepare. It does not promise anyone a place.
The big round of 2004
The largest wave came on 29 March 2004, when Bulgaria, Estonia, Latvia, Lithuania, Romania, Slovakia and Slovenia joined. They had been invited at the Prague Summit in 2002, and all seven had taken part in the MAP first.
After that the pace slowed. Albania and Croatia became members on 1 April 2009, having signed their accession protocols the previous July. Montenegro followed on 5 June 2017. North Macedonia had to settle its name dispute with Greece first; the Prespa Agreement of 2018 cleared the way, and on 27 March 2020 it became NATO’s 30th member.
Finland and Sweden
For decades Finland’s cooperation with NATO rested on military non-alignment and a firm national consensus. Russia’s full-scale invasion of Ukraine in 2022 ended that. Finland and Sweden both sent their application letters on 18 May 2022, were invited at the Madrid Summit on 29 June, finished accession talks on 4 July and signed protocols the next day.
Finland deposited its instrument of accession on 4 April 2023 and became the 31st member. Sweden, which had also been a Partnership for Peace participant since 1994, deposited its own on 7 March 2024.
The 1997 Founding Act
Enlargement was never a purely Western affair. On 27 May 1997 in Paris, Boris Yeltsin joined Bill Clinton and the leaders of the 15 other NATO states to sign the Founding Act on Mutual Relations, Cooperation and Security. NATO foreign ministers had decided in December 1996 to seek the deal mainly to soften the damage that enlargement was doing to relations with Russia. The Act created a NATO-Russian Permanent Joint Council and carried a qualified pledge not to deploy nuclear weapons or station troops in the new member states. NATO said it would defend its members by interoperability and reinforcement rather than by “additional permanent stationing of substantial combat forces.”
Almost nobody agreed on what that meant. Washington officials stressed the Act was politically, not legally, binding. Henry Kissinger feared it would dilute the Alliance. In Moscow, Gennady Zyuganov, the Communist leader, called it a “complete and unconditional surrender”, and Yeltsin warned that NATO would “fully undermine” relations if it took in any former Soviet republic. National Security Advisor Sandy Berger answered that no nation “should be excluded” if it met the criteria and sought membership.
That argument over who may join, and what it costs, is still running.
Sources
- NATO member countries | NATO Topic
- The NATO Russian Founding Act | Arms Control Association (Arms Control Today, Jack Mendelsohn)
