On Wednesday, Finland and Sweden formally submitted their applications to join NATO.
Only a few months ago, that would have seemed almost unimaginable. Both countries had spent decades outside the alliance, maintaining military non-alignment while cooperating closely with Western institutions. Russia’s invasion of Ukraine changed that calculation with extraordinary speed. Finland concluded that neutrality no longer provided sufficient security. Sweden followed the same path. Public opinion shifted, governments changed policy, and two of Europe’s most established non-aligned states decided that Article 5 was now more valuable than remaining outside the alliance.
At NATO headquarters, Secretary-General Jens Stoltenberg called it a historic moment.
Then Turkey said no.
President Recep Tayyip Erdoğan has objected to the applications, arguing particularly that Sweden and, to a lesser extent, Finland have tolerated or supported organisations Turkey considers terrorist groups. Ankara has repeatedly focused on the Kurdistan Workers’ Party, the PKK, and Syrian Kurdish organisations that Turkey regards as closely connected to it. Erdoğan has also criticised restrictions on defence exports to Turkey and demanded changes from the Nordic states before Ankara will approve their entry.
Because NATO operates by consensus on enlargement, Turkey does not need to persuade most of the alliance.
It needs only to refuse.
That makes this week an unusually clear demonstration of something we often forget when talking about alliances: alliances are not friendships between countries that agree about everything. They are bargaining institutions among states whose interests overlap enough to cooperate but never become identical.
Finland and Sweden assumed their applications would be welcomed because, from the perspective of most NATO members, they appear unusually attractive candidates. Both are stable democracies with capable militaries, sophisticated economies and long histories of cooperation with the alliance. Finland shares a very long border with Russia, and both countries occupy strategically important positions around the Baltic Sea. Their membership would probably strengthen NATO militarily rather than simply extend protection towards weak new members.
Most NATO governments therefore see enlargement primarily through the lens of Russia.
Turkey sees something else.
For Ankara, the Kurdish issue is one of the central national-security questions of modern Turkish politics. The PKK has conducted an armed insurgency against the Turkish state for decades and is designated a terrorist organisation not only by Turkey but also by the European Union and United States. Turkey additionally regards the Syrian Kurdish YPG as essentially an extension of the PKK, while several Western governments have distinguished between the two and worked with YPG-linked forces against Islamic State in Syria.
That divergence has produced years of tension inside NATO.
Sweden in particular has maintained relationships with Kurdish political organisations and accepted refugees and political exiles whom Turkey views with suspicion. Ankara argues that an alliance organised around collective security cannot reasonably ask Turkey to approve countries that, in Turkey’s view, fail to treat threats to Turkish security seriously. Erdoğan has therefore framed his objection not as obstruction but as a demand for reciprocity.
If NATO members expect Turkey to take Finnish and Swedish security concerns seriously, Turkey argues, Finland and Sweden must take Turkish concerns seriously too.
That argument should not simply be dismissed as opportunism.
Turkey has genuine security concerns.
But timing creates obvious questions about leverage.
These disputes did not suddenly appear this week. Turkey could have raised them through bilateral diplomacy previously and frequently did. What changed is that Finland and Sweden now urgently want something Turkey can withhold.
That transforms an existing disagreement into bargaining power.
In game-theoretic terms, Turkey’s outside option has improved. It can block enlargement at relatively low immediate cost while Finland and Sweden face substantial incentives to obtain approval quickly.
This is what veto power does.
It converts a country’s willingness to say no into political capital.
At first, that seems deeply inefficient. Why should one NATO member be able to obstruct a decision supported by twenty-nine others?
The answer reveals the purpose of consensus institutions.
NATO is not a supranational government in which countries accept majority rule over national security. It is an alliance of sovereign states making extremely serious commitments to one another, including the possibility of going to war if another member is attacked.
That kind of commitment requires consent.
Imagine NATO could admit a new member through simple majority vote. Sixteen states could extend Article 5 to a new country while fourteen objected. Those fourteen would then supposedly become obligated to participate in collective defence for a commitment they explicitly rejected.
The guarantee would immediately become less credible.
Unanimity therefore protects the credibility of the obligation.
Every member knows that any new commitment exists because every existing member formally accepted it.
The price is that every member acquires leverage.
This is a recurring institutional trade-off.
A veto prevents majorities from imposing unacceptable outcomes on minorities.
It simultaneously allows minorities to block outcomes that majorities consider necessary.
The United Nations Security Council has the same problem in a much more extreme form. Permanent-member vetoes make collective action difficult, especially when one of those members is itself involved in a crisis. Yet those vetoes were partly the price required to keep major powers inside the institution after the Second World War.
Institutions often survive not because their rules are perfectly efficient but because the rules make participation acceptable to the actors whose participation matters most.
NATO’s consensus rule operates through similar logic.
Turkey may frustrate almost every other member this week.
But Turkey also controls the Bosporus and Dardanelles, maintains one of NATO’s largest militaries, borders the Black Sea region, sits between Europe and the Middle East and occupies an extraordinarily important strategic position relative to Russia.
An alliance cannot treat Turkish interests as irrelevant simply because Turkey is currently inconvenient.
This is where alliance politics becomes much less sentimental than speeches about shared democratic values suggest.
Turkey is a NATO member.
It is also governed by Erdoğan, whose domestic politics have become increasingly authoritarian and whose foreign policy frequently diverges from Washington and European governments. Turkey purchased the Russian S-400 air-defence system despite fierce American objections. It has fought Kurdish groups supported by Western states in Syria. It maintains complicated relations with Russia, Greece, Cyprus and the EU.
Yet NATO continues to consider Turkey strategically indispensable.
That demonstrates again that alliances are constructed from interests and capabilities as well as values.
If NATO were purely a club of liberal democracies with identical foreign policies, Turkey’s position would be easier to evaluate.
It is not.
It is a military alliance whose members share a central commitment while disagreeing over many other issues.
This makes Erdoğan’s veto both frustrating and institutionally normal.
The more difficult question is whether Turkey is using the mechanism in good faith.
There is a difference between saying, “These applicants create direct security concerns that need resolution before we extend them a defence guarantee,” and saying, “We possess a veto, so we will use it to extract unrelated concessions.”
International institutions rarely contain an objective referee capable of determining the difference.
Every country describes its own interests as legitimate.
Others describe the same behaviour as transactional when it becomes inconvenient.
This is why bargaining matters.
Finland and Sweden may offer changes in policy towards Kurdish organisations, review defence-export restrictions or provide clearer assurances about counterterrorism cooperation. Turkey may then conclude that its objections have been sufficiently addressed.
The final agreement, if one emerges, will probably look less like one side proving the other wrong and more like an exchange.
That is normal diplomacy.
The interesting part is what the exchange reveals about relative bargaining power.
Finland and Sweden possess strong political support from most NATO members.
Turkey possesses a veto.
Those are different forms of power.
One is coalitional power.
The other is pivotal power.
A small or isolated actor can sometimes become extraordinarily influential because its agreement is necessary to complete a coalition.
This resembles the coalition politics I wrote about after Germany’s election. A party with 10% of parliamentary seats can become decisive if neither large party can govern without it.
Turkey is much larger and more strategically important than a minor coalition partner, but the structural mechanism is similar.
Power depends not merely on size.
It depends on whether the system can proceed without you.
This is one reason political institutions frequently produce outcomes that look disproportionate when judged only by population or economic weight.
Luxembourg can have a formal role in an EU decision despite being tiny compared with Germany.
A senator from a small US state can possess the same Senate vote as one representing tens of millions of people.
A minor parliamentary party can determine who becomes prime minister.
Turkey can block two Nordic countries from entering NATO.
Institutional rules create power in addition to distributing it.
That power can be annoying when used by somebody else.
It is often the same protection you may eventually need yourself.
Finland should understand that particularly well. Helsinki wants to join NATO precisely because institutional commitments matter. It wants a treaty rule saying that an attack on Finland is treated as a concern for the entire alliance.
That rule constrains twenty-nine other countries.
Finland cannot reasonably demand the benefits of rigid institutional commitment while complaining that existing members possess rigid institutional rights during admission.
The same institutional seriousness makes both possible.
This does not mean Turkey should be free from criticism.
Its claims need evidence, and demands should be proportionate. Labelling broad categories of Kurdish political activism as terrorism risks collapsing distinctions between violent organisations and legitimate political expression. Democratic states should be extremely cautious about extraditing individuals to another government simply because that government labels them security threats.
The rule-of-law questions are real.
Sweden cannot simply hand over political refugees or residents because Ankara demands it if Swedish courts and law do not permit extradition.
This creates another tension between alliance bargaining and domestic legal institutions.
A government may want to make a concession internationally and discover that its own courts constrain what it can offer.
That is not necessarily weakness.
It is constitutional government.
Foreign policy in democracies occurs inside law.
Erdoğan may find that frustrating because he is bargaining with governments that cannot always deliver every requested outcome through executive decision alone.
Again, institutions affect negotiation.
This makes the coming talks more complicated than Turkey listing demands and Sweden accepting them.
Swedish and Finnish governments will need to find concessions consistent with their own legal systems and political values.
Turkey will need to determine which concessions are enough.
Other NATO members will probably pressure both sides because they consider rapid enlargement strategically important.
The result will reveal how alliances manage internal disagreement while facing an external threat.
That last part is important.
Russia’s invasion of Ukraine is what produced Finland’s and Sweden’s applications in the first place.
Moscow has therefore created a strategic opportunity for NATO enlargement, but internal alliance politics may delay or reshape the result.
This reminds us that organisations should not be treated as unitary actors.
We often write “NATO decided” or “the EU wants” as though institutions have one mind.
They do not.
NATO contains thirty governments, each with domestic politics, security concerns and bargaining objectives.
Alliance unity does not mean preference uniformity.
It means members have developed institutions capable of producing common action despite preference differences.
This is a much higher standard.
In some ways, disagreement can demonstrate institutional strength because countries feel secure enough inside the alliance to assert national interests openly.
The real test is whether disagreement can ultimately be resolved without undermining the core commitment connecting the members.
Turkey’s relationship with Russia demonstrates the complexity particularly well. Ankara has condemned Russia’s invasion and supplied Ukraine with Bayraktar drones. It has also avoided joining Western sanctions and continues speaking with Moscow. Turkey has attempted to mediate between Russia and Ukraine while maintaining relationships with both.
That is not necessarily inconsistency.
Turkey’s geography and interests encourage strategic flexibility.
It depends on Russia in some economic areas, competes with Russia in others, opposes Russian influence in certain regional conflicts and still needs cooperation on issues such as Syria and energy.
States rarely fit perfectly inside alliance blocs.
Turkey may be a NATO member without wanting every relationship determined by NATO’s confrontation with Russia.
India operates through a somewhat similar logic outside formal alliances: close strategic cooperation with the United States while maintaining significant defence and political ties with Russia.
Middle powers often attempt to preserve multiple relationships because dependence on a single major power reduces autonomy.
That strategy can frustrate allies.
It can also increase bargaining leverage.
Turkey’s current position demonstrates this dramatically. NATO wants Turkish approval for enlargement. Russia wants to prevent enlargement. Finland and Sweden need Ankara. Western governments also need Turkey for Black Sea security and regional diplomacy.
Turkey sits at the intersection.
Geography has given Ankara considerable strategic relevance.
Institutions have given it a veto.
Erdoğan is using both.
The easiest response would be to complain that one country is holding the alliance hostage.
There is some truth in that description.
But perhaps the more useful lesson is that collective-security institutions are built on voluntary commitments among sovereign states, and sovereign states do not stop pursuing national interests after joining.
NATO works not because thirty countries become one political community.
It works because their interests overlap enough on one extraordinarily important question: defending one another against major external threats.
Everything beyond that remains negotiable.
The challenge is ensuring those secondary disagreements do not destroy the primary commitment.
Finland and Sweden are applying because Russia’s invasion convinced them that NATO’s commitment is credible enough to be worth abandoning decades of non-alignment.
Turkey’s objection demonstrates why that credibility is expensive.
Every existing member has to consent to extending the promise.
From the outside, unanimity looks inefficient.
From the inside, it is part of what makes the promise believable.
The next stage will therefore be bargaining.
Turkey will demand changes.
Finland and Sweden will decide which changes they can accept.
Other allies will pressure Ankara and perhaps the applicants.
Eventually, either a compromise emerges or the applications remain blocked.
As of tonight, we do not know which.
What we already know is that Russia’s invasion has achieved something extraordinary: it persuaded two historically non-aligned European countries to request admission into NATO.
And Turkey has achieved something equally revealing: it reminded everyone that wanting to join an alliance and being entitled to join it are not the same thing.
Collective security depends on solidarity.
It also depends on consent.
Sometimes the country saying no possesses more power than the twenty-nine saying yes.
