The U.S. Senate’s 95-1 vote in favor of Finland’s and Sweden’s accession to NATO is a major step toward full alliance membership of these important Nordic partners. With only seven of NATO’s 30 members left to ratify, Sweden and Finland could be NATO members before the end of the year.

The Senate’s overwhelming support reflects strong bipartisan agreement that Sweden and Finland will add great value to the alliance. They are militarily advanced and technologically savvy. Each country’s regional expertise on Russia and traditions of “total defense” will also add to NATO’s understanding of Northern European security challenges and ways in which allied societies can build resilience against disruptive threats.

The addition of Sweden and Finland will connect the entire High North outside of Russia in one of NATO’s strategic spaces, raising the threshold of risk for Russia should it contemplate further aggression. They will more than double the number of Nordic fourth- and fifth-generation fighters available to NATO. Accession will facilitate NATO defense of the Baltic states, which is currently constrained through a sliver of territory along the Polish-Lithuanian border known as the Suwalki Gap. Supply and support of the Baltic states by new Baltic Sea allies will enhance those countries’ ability to defend themselves.

But Sweden and Finland are not joining an alliance waiting at the station; they are boarding a moving train.

In June, NATO leaders already unveiled a new Strategic Concept that broadly charts the alliance’s next decade. They agreed to a fundamental shift in NATO’s deterrence and defense posture. They committed to invest more in defense, increase common funding, offer comprehensive support for Ukraine, address challenges posed by China, and advance a NATO Innovation Fund and a Defense Innovation Accelerator to help the alliance sharpen its technological edge. Sweden and Finland will be expected to sign up to these initiatives. And now NATO will need to implement its decisions with two new allies in mind.

Allies at Madrid essentially agreed that NATO must move away from its current posture of tripwire defense and provisions for reinforcement to forward defense and deterrence by denial — the operational implication when allied leaders say they will “defend every inch” of NATO territory. These commitments, coupled with Finnish and Swedish membership, require allies to develop a robust, integrated, multidomain Nordic-Baltic defense posture.

On the ground, allies at Madrid resolved to transform the relatively light presence of rotational, multinational forces deployed in the Baltic states and Poland into multidomain forces at the brigade level, and to station forward munitions and heavy material such as artillery. They committed to generate a “New NATO Force Model” intended to organize and mobilize up to 800,000 troops, 300,000 of which would be able to mobilize within 10-30 days.

These changes will require even more North American and European troops deployed to NATO’s eastern front, new infrastructure by host nations to receive those troops, a new command structure, and a revised concept for military operations. Not only will Sweden and Finland be expected to contribute directly to these efforts, but their accession opens new terrain for allied reception and staging operations, recasting Norway’s traditional role.

In the air, two important shifts are required. First, NATO should move to establish a new Nordic air operations center for air missions across the region. NATO air forces have exercised regularly with those of Sweden and Finland, and cross-border training arrangements are already in place. But full integration was not possible. Nordic allies now need to share radar and sensor data and conduct battle planning together.

Second, allies have supplemented their ongoing Baltic air-

cing missions with “air shielding” operations that add air- and ground-based missile defense assets, and place them under NATO command. Sweden and Finland should join those operations upon accession.

Allies also need to strengthen their maritime presence in the Baltic Sea region. At Madrid, allies agreed to strengthen their maritime posture and situational awareness. They will need to update their Maritime Strategy, which is over a decade old, and thus does not take into account Swedish or Finnish membership, despite a history of joint exercises. MARCOM, NATO’s maritime component command based in the U.K., is slated to move forward cells for the Baltic Sea and the Black Sea to headquarters in each region. Germany and Poland are each vying to host the Baltic headquarters, yet it remains unclear whether such an entity would actually command multinational forces or simply monitor developments and enhance situational awareness. There is still much to be sorted out.

All of these plans are heavily reliant on allies’ ability to move forces quickly forward across allied territory. Procedures for crossing borders need to be simplified and aligned, logistical hurdles must be addressed and transport infrastructure needs to be upgraded. The European Union’s military mobility initiative, which also includes the United States, Canada and Norway, was intended to address these challenges. Yet the initiative has stalled; in the EU’s 2021-2027 budget, the project’s funding was slashed from a proposed €6.5 billion (U.S. $6.62 billion) to just €1.7 billion (U.S. $1.73 billion). And while EU leaders agreed in March 2022 to accelerate these efforts, little progress has been made.

Now that EU members Sweden and Finland are joining NATO, and NATO member Denmark in June abandoned its long-standing opt-out from the EU’s common security and defense policy, Nordic pressure should be mobilized to accelerate military mobility.

Ultimately, however, the true test of Finnish and Swedish accession may be the degree to which these two new allies are prepared to support the alliance’s “360 degree” approach to defense, which means not only countering challenges from Russia in the north, but also addressing pressures emanating from NATO’s south and southeast.

Moreover, at Madrid, allied leaders underscored that NATO’s ability to address traditional and unconventional threats in Europe is becoming intertwined with related challenges to alliance security interests posed by China. It will be critical for Sweden and Finland, two technologically advanced countries, to work with other allies to bolster protection of defense-critical infrastructures and defense-related supply chains; enhance investment screening of foreign investment in security-related infrastructures, companies and technologies; and help NATO make good on its pledge to chart a road map for enhanced cooperation with Australia, Japan, New Zealand and South Korea.

This is an ambitious but realistic agenda. We should embrace it.

Daniel S. Hamilton is senior nonresident fellow at the Brookings Institution and a senior fellow at the Foreign Policy Institute of Johns Hopkins University’s School of Advanced International Studies. He previously served as U.S. deputy assistant secretary of state responsible for NATO and Nordic-Baltic affairs.

More In Commentary