Finland and Sweden have now applied for NATO membership, and the process of bringing them on as full members of the alliance is accelerating into what may become the quickest turnaround ever. Research by international relations scholars (including me) suggests that the alliance needs to work out and agree on a military plan for defending them as soon as possible—before the two Nordic countries join.

Paul Poast
Paul Poast is an associate professor in the Department of Political Science at the University of Chicago and a nonresident fellow at the Chicago Council on Global Affairs.

On the one hand, there are plenty of reasons why the two nations have a strong case to join the alliance. Finland brings much to the NATO table. Prior to the war in Ukraine, Finnish defense spending, as a percentage of GDP, was already moving toward NATO’s 2 percent target, with further increases planned. Finland also has a conscription policy, which is often seen to demonstrate to allies a strong commitment to self-defense against a potential Russian attack. Similarly, Sweden has long worked with NATO, including covert cooperation during the Cold War and assistance with peacekeeping operations thereafter. Since the defense of Finland is a pillar of Sweden’s defense policy, it also is sensible for Stockholm to follow its neighbor into the alliance. Since both nations are EU members, one could argue that they essentially gave up their military neutrality long ago. Moreover, both nations are strong democracies, a core principle of the alliance (if not always followed in practice).

On the other hand, there are concerns. In the case of Finland, these concerns range from increasing NATO’s direct border with Russia to detracting from the development of the EU as a security provider independent of the United States. With respect to the latter, Hanna Ojanen of the University of Tampere notes that because “NATO membership would absorb quite some energy for the years to come,” it might have been preferable for Finland to “have used that energy for EU security and defense.” Still others have objected on broad geopolitical grounds.

While political momentum may make these membership bids inevitable, the ultimate effects of bringing Finland and Sweden into the alliance depend on making sober decisions before they enter. Specifically, NATO allies must have a plan for defending the two countries. The two Nordic countries’ defense cannot rest alone on the perceived sanctity of NATO’s Article 5 defense commitment or on a vague plan to address the issue later.

What’s the Plan?

To be effective, alliances need to have hard discussions about war plans. Who will the allies defend and how will they do so? Do the prospective new members agree with existing NATO allies on who constitutes a threat and where? Do the two groups have similar visions for how to address the threat Russia poses if the situation becomes acute? Are their military doctrines compatible? These are pivotal questions for all alliances.

When states form an alliance, the final treaty is commonly short on war-planning specifics. But discussions over aspects of war plans often consume a fair amount of time and energy during such negotiations. Indeed, disagreements over these issues can ultimately undermine an alliance’s formation. If a state does not see the potential alliance as adequate for meeting its security aims, it can look elsewhere. This most infamously occurred in August 1939. The Soviet Union, frustrated over an inability to agree with the United Kingdom on how best to counter a potential German attack, left the Anglo-French-Soviet defense treaty negotiations. It then signed a nonaggression pact with Nazi Germany.

Hard bargaining over the defense practicalities of a potential alliance treaty was also part of the creation of NATO itself.1 Far from a given when the alliance treaty was negotiated in 1948 and 1949, there were endless arguments about how to define the North Atlantic region in the first place. This definition turned out to be critical at the strategic level of war planning: before one can talk about logistics and tactics, one must decide who should actually be protected. The talks nearly broke down over debates about whether to include Norway (France was opposed), Italy (U.S. and British officials were skeptical), or Algeria (then a French department). Wanting to ensure that a deal was reached, the parties made compromises: Norway and Italy were included, and Algeria was indeed covered (until it gained independence, at which point the North Atlantic Treaty was amended). While details over executing the actual defensive procedures were delegated to a soon-to-be-created body (the “O” of NATO), the perception was that there was time to figure it out. Communism was a threat, but there was no perception of an immediate Soviet invasion.

While a failure to settle logistical and operational details might have been understandable when NATO was formed, the truth is that planning for the defense of prospective new members continued to be neglected, including in recent decades. Consider the closest parallel to Finland’s accession, that of the Baltic states. Even in the 1990s, before Estonia, Latvia, and Lithuania became official candidates for NATO membership, the states were seen as largely indefensible, in purely military terms, from an operational and tactical standpoint. No solutions to this challenge were pursued until well after their entry into the alliance. NATO members chose to overlook the lack of a solution when they admitted the Baltic states in 2004, on the grounds that the alliance ought to support fledgling democracies that had demonstrated their value through peacekeeping operations. More importantly, at that time Russia did not pose an imminent threat.

This defensive shortcoming was eventually corrected, so to speak, in the wake of Russia’s 2014 invasion of Ukraine by the creation of NATO’s Enhanced Forward Presence. Like the 2014 Wales Summit pledge that NATO members made to increase their military spending, the Enhanced Forward Presence was motivated by Russia’s 2014 annexation of Crimea. The threat of armed aggression, long a concern of the Baltic states, had now been realized. For the Baltic states and other members of NATO’s eastern flank, there was a window of opportunity to adjust. No such window is obvious in the case of Finland.

Where Are the Troops?

Planning is about more than just paper reports and memoranda to be filed away and dusted off when the time arrives. It is about ensuring that the proper resources are being developed and deployed to execute a plan. One such issue that NATO members must decide as soon as possible is whether to position forces in Finland and Sweden and, if so, how many. Even if alliance members opt not to pre-position forces in the two Nordic countries, they will have to determine where the forces that would be used for their defense will come from.

Russia’s military is being weakened by the war in Ukraine and has displayed shortcomings that few analysts predicted. It will take time for Russian forces to recover, but eventually they will probably still be capable of “fait accompli” operations against some section of Finnish or even Swedish territory. This would involve quickly moving forces into an unprotected or lightly protected portion of territory, thereby compelling the other side to take offensive action in order to reverse the territorial acquisition. Concerns over such an operation against Finland are heightened by its 800-plus-mile border with Russia. While Finland has approximately 3,000 personnel in its border guard, these forces are oriented primarily toward enforcing immigration control rather than stopping an invading force. When coupled with Russia’s threats, this force positioning creates a precarious state of existing defenses along that border.

As the creation of the Enhanced Forward Presence implies, NATO’s Article 5 does not automatically deter aggression. This is because, to use the language popular among international relations scholars, it ultimately does not “tie hands.” It is true that Article 5 obligates alliance members to treat an attack in North America or Europe on one or more members as “an attack against them all,” but the text goes on to say that each member will then assist “by taking forthwith . . . such action as it deems necessary.” Practically, this means that for each NATO member and the alliance as a whole, Article 5 is more appropriately viewed as specifying something akin to saying an attack on one merits a response to be determined by the individual members. Concretely, once the North Atlantic Council determines that an attack meriting an Article 5 response has occurred, the members decide on the appropriate response and then individual members decide how they will contribute to that response. Since NATO decisionmaking is predicated on consensus, meeting the first two thresholds for an Article 5 action is never guaranteed.

Of course, failure on the part of the NATO allies to assist a member under attack could carry reputational consequences; if Russia were to witness a nonresponse to a quick incursion into, say, the Baltic states, then Moscow might be emboldened to take further measures. But the likelier problem is that NATO may respond meekly. The space between a nonresponse and full-fledged direct military engagement by all NATO members against the aggressor is wide enough to allow for a host of options that meet the letter of Article 5’s terms without changing the military facts on the ground.

This is why, as illustrated by the Enhanced Forward Presence, deterrence requires “sinking costs,” meaning forward deploying troops on NATO territory before an attack occurs. But for this approach to be effective, it cannot be done lightly. The forces must not be merely a tripwire, where a few troops are deployed with the understanding that their deaths would trigger a larger response. Such a policy would be too slow to stop a fait accompli operation and would run again into the problem that Article 5 does not obligate any particular type of action.

Instead, forces need to be deployed in large enough numbers to have a material impact on the aggressor’s battle plan. Ideally, the forward-deployed NATO forces would be sufficient to tip the local balance of power in favor of the defender so as to deny territory to the aggressor. At a minimum, they should be enough to slow down the aggressor’s strike, preventing the invading forces from securing territory before the defender’s reinforcements could arrive. This assumes that foreign forces would even be allowed on Finland’s territory. That is not yet clear.

Hard Conversations

Given that Finland’s membership process is proceeding swiftly, that NATO is actively and heavily supporting Ukraine’s fight against Russia, and that NATO bureaucrats are busy crafting a new Strategic Concept, there is little space right now for hard conversations on the above points. This is unfortunate, as the lack of conversation could start the new relationship off on precarious footing.

One step for NATO to take is obvious: deploy forces, immediately. Unlike during past NATO membership expansions, time is not on the alliance’s side here. If it’s too late for pre-planning, then NATO must quickly move to reposition troops into the alliance’s new northeastern flank. If the NATO allies are not willing to commit new troops, this could be achieved by repositioning existing forces. Alternatively, perhaps this is the time for the EU itself, given that Finland and Sweden are both members, to fully commit to being a security provider. The EU could fill the gap in force deployments by encouraging its members to move forces to the Finnish-Russian border, potentially leveraging NATO’s command and control capabilities. Given that the contributions to the Enhanced Forward Presence are shared in a fairly equitable fashion among various NATO members, perhaps this approach can be duplicated in Finland.

However, under the current structure of NATO, the United States is the ultimate backstop for such deployments, and it will ultimately fall on Washington to fill in any gaps in forces for Finland. This is problematic. Though U.S. President Joe Biden and his administration strongly support Finland’s and Sweden’s bids to join NATO, it is unclear that the Biden team, or any future U.S. administration, is willing to base sizeable deployments of U.S. forces on Finnish territory.

To further complicate matters, forward deploying troops on Finnish territory would not be a short-term commitment. Even if the war in Ukraine grinds to a halt, Russia will probably retain or rebuild its ability to carry out quick incursions against its neighbors, which would then include a Finland within NATO. Defending Finland will require a long-term and concrete plan involving the deployment of substantial forces. Such a commitment would not come without costs, both in terms of budget expenses and the potential diversion of troops from other theaters.

Additionally, questions should be asked about how Finland and Sweden will contribute to the defense of NATO territory beyond their own borders. Their presence alters NATO’s map. Whether that alteration is a net positive or negative for the alliance depends on exactly how Sweden’s and Finland’s forces are used. While they have a track record of working alongside NATO members in operations outside NATO territory, will they, for example, assist with the Enhanced Forward Presence? How exactly will they balance Russian operations in the Arctic? These questions must be faced in the rush to add Finland and Sweden to NATO.


1 This paragraph draws from Chapter 5 of the author’s book. See Paul Poast, Arguing About Alliances: The Art of Agreement in Military-Pact Negotiations (Ithaca, NY: Cornell University Press, 2019).