Those (few) commentators who seek to justify, or at least explain, Russia’s invasion of Ukraine usually cite the expansion of Nato as the underlying reason. They claim that Russia feels betrayed by the failure of the US and its allies to honour a promise—given in the context of the re-unification of Germany—that the North Atlantic Alliance would not offer membership to the countries of central and eastern Europe that had formerly belonged to the Warsaw Pact.
No such promise was ever written down. The document recording the so-called Two Plus Four agreement—under which the US, the Soviet Union, the UK, France and the two Germanies agreed the terms of German re-unification—contains provisions about Nato’s military dispositions in the former German Democratic Republic, but nothing about Nato’s future relationship with other states. There had, however, been previous conversations between various Nato leaders and Soviet president Mikhail Gorbachev that would have given the impression that an enlargement of Nato to the east was not on the cards, and that the Soviet Union’s security concerns would be taken into account.
When the North Atlantic Alliance was established in 1949, it had 12 members. It regularly expanded over the subsequent years and now has 30. Following the end of the Cold War in 1990, the Czech Republic, Hungary and Poland joined in 1999; Bulgaria, Slovakia, Slovenia, Romania and the three Baltic states in 2004; Albania and Croatia in 2009; Montenegro in 2017; and North Macedonia in 2020. It will expand again in the coming weeks or months as Finland and Sweden join. Both these countries will be assets to Nato. They are mature democracies with highly capable armed forces, which have for many years integrated themselves into Nato’s operational doctrines and procedures. Finland’s over 800-mile border with Russia will now be Nato’s longest stretch of frontline territory. But defending it will rely principally on Finland’s own armed forces, which are large and can rapidly mobilise.
Finnish and Swedish membership will also change the balance of forces in the Baltic Sea, which will now become effectively a Nato lake. Hitherto the Russian air force has made a point of frequently violating Finnish and Swedish airspace in the Baltic. It may be less keen on doing so if this would mean a wider potential confrontation with other Nato air forces.
Under Article 10 of the North Atlantic treaty, existing members may invite any other European state to join if it is in a position to further the treaty’s principles and to contribute to the security of the North Atlantic area. At a summit meeting in 2008, it was agreed that Georgia and Ukraine would become members at some unspecified date in the future. In 2010, Bosnia and Herzegovina was invited to join the Membership Action Plan, which is normally a precursor to membership. Moldova, which borders Ukraine, is committed to neutrality and currently has no aspiration to join Nato, but it is not inconceivable that it might seek to do so in the future. The same is true of Serbia, although attitudes to Nato there are clouded by the experience of being bombed by Nato forces in 1995.
Whether any of these countries will ever actually be invited to join is an open question. A report in the 1990s laid out certain criteria for enlargement (democracy, commitment to the peaceful settlement of disputes, etc), but didn’t mention one which has been informally applied, namely that the alliance should not take on members who have current territorial disputes. So long as parts of what Georgia regards as its territory (South Ossetia and Abkhazia) are under Russian control, it is hard to see how Nato could credibly undertake a commitment to defend it.
The same applies of course to Ukraine. However much sympathy there may be for Ukraine elsewhere in Europe (and Eurovision suggests that it does indeed enjoy widespread popular support), few other governments would be willing to commit their own forces to the liberation of Donbas or Crimea. But some Nato politicians, for example the French president, the German chancellor and the US defense secretary, are now proposing a ceasefire without any withdrawal of Russian forces from the occupied parts of Ukraine. Were Ukraine to accept this (of which there is no sign so far), they presumably hope that it might become the basis of a permanent settlement. If so, Nato should follow the logic of its own position and offer Ukraine Nato membership.
