Russia's designs on expanding its territory in Ukraine have been a boon to NATO expanding its own. The full-on invasion in February 2022 was the final nail in the coffin of longstanding neutrality for Finland and Sweden. The northern European countries, on Russia's doorstep, joined the US-led military alliance in 2023 and 2024, respectively.
The alliance's "open door policy” is part of its founding treaty, the 1949 Washington Treaty, which turned 75 in the spring. It allows “any other European state in a position to further the principles of this Treaty” to apply for membership, provided that existing members have unanimously agreed to extend an invitation to join.
It's a strength-in-numbers principle, which means there are “more resources, more defence forces and more opportunities,” Nele Loorents, a research fellow at the Tallinn-based think tank International Centre for Defence and Security (ICDS), told The Parliament.
NATO now at 32 members — and counting?
Since NATO is as much a political alliance as a military one, candidate countries must also be democracies with market economies and committed to the rule of law.
Joining means commitment to the Washington Treaty, especially Article 5, which stipulates that an attack on one member is an attack on all. Each member decides for itself how it can contribute to collective defence. Direct military intervention is just option. An ally could instead provide logistical or intelligence support, or impose sanctions on the aggressor.
Bringing a new country into the alliance can take years of alignment, which requires adjustments on both sides. For NATO, it means “there's a new military to integrate, to learn about, to understand how it's structured, what military capabilities it possesses,” Max Bergmann, director of the Europe, Russia, and Eurasia Program at the Center for Strategic and International Studies (CSIS), a Washington-based think tank, told The Parliament.
New members are also expected to adhere to the 2% spending guideline, which was introduced in 2014. As of this year, 23 members are expected to spend at least 2% of their GDP on defence, according to NATO figures. Newbies Sweden and Finland are among those to check the spending box.
Russia hangs over Ukraine’s membership
The Swedish and Finnish accession process may seem like a breeze in comparison to the next countries on the list of getting a seat at the transatlantic table. Chances are low that Ukraine or Georgia will become the 33rd member any time soon.
Despite NATO overtures to Ukraine, most recently at its July summit in Washington DC, Russia’s full-scale invasion complicates the process. Russian troops are also occupying parts of Georgia, and the country has marked a shift towards more Kremlin-friendly policies. Located on the far side of the Black Sea, Bergmann said it could also be difficult for NATO to defend.
The difficulties underscore how much the accession timetable can vary depending on the country trying to join. But even for Finland and Sweden, established democracies with modern armed forces largely up to NATO standards, there was a process to be followed.
It starts with approval by the North Atlantic Council, NATO's political decision-making body, which consists of representatives of each member state. All members must approve the invitation.
“It's about trust. It's about unity. It's about solidarity. It's about common understanding. And that's the way how NATO has been set up,” Loorents from ICDS said.
Unanimity might make the decision-making process longer, but it ensures that each member has its say. “Otherwise, it can happen that bigger allies or stronger allies can push down the interests of smaller allies,” she said.
Mapping out the path to NATO membership
Once invited, accession talks can begin at NATO headquarters in Brussels. This ensures that the candidate country can meet NATO obligations. These are agreed to in a letter of intent. Any reforms required must be completed within an agreed upon timetable.
“There's a number of very nitty-gritty technical military steps that have to be taken,” Bergmann said, such as for military equipment and intelligence processes.
Before Estonia joined in 2004, the Baltic country had to modernize its defence forces and adopt NATO standards to help ensure interoperability. This meant phasing out the Soviet-era equipment it had from the Cold War, when it was part of the USSR.
In a final step, the legislatures of existing members have to ratify accession protocols for the invited country. It's at this stage that an otherwise technical and bureaucratic process can get political.
When it came to Finland and Sweden, Turkey and Hungary put up a fight. Finland faced less resistance, allowing it to join in early 2023, but Sweden’s process dragged out for another year. Turkey wanted to see Sweden take a tougher stance against Kurdish groups that it considers terrorists. Budapest didn’t like Stockholm’s criticism of Hungary’s democratic backsliding.
Once outstanding issues such as these get resolved, however, the protocols are accepted by NATO members. That allows the alliance’s secretary-general to invite the new countries to formally join.
Only then is the deal is done and dusted, but the hard part may have only just begun: Making 32 militaries operate as one.