Sweden is not a member of NATO. But Sweden is very important to the defense of NATO’s Baltic member countries of Estonia, Latvia, and Lithuania. That importance mainly stems not from what Sweden could add to NATO’s collective military strength, but from how its strategic position could help NATO overcome the operational challenges it would face if it needed to respond to a Russian invasion of the Baltics.
Strategic Position in the Baltic Sea
Spanning the length of the Scandinavian Peninsula, Sweden’s geography dominates much of the Baltic Sea, a fact that NATO has long appreciated. Early on in the Cold War, NATO recognized that Sweden could serve as a valuable location for early warning facilities to monitor the Soviet Union in peacetime and for combat aircraft to interdict Soviet lines of communications across Germany and Poland in wartime.
Sweden took on a new relevance for NATO after Estonia, Latvia, and Lithuania joined the Alliance in 2004. With tiny military forces of their own and large Russian military forces on their borders, the three Baltic countries are highly vulnerable. Russia could easily sever their air and land connections to the rest of NATO and capture all three countries—a prospect that could jeopardize the very existence of NATO. Thus, NATO holds annual exercises called Baltic Operations (Baltops), in part, to practice reinforcing the Baltics by sea. But, in a conflict, Russian strike aircraft and coastal defense missile batteries based near Kaliningrad could interdict such seaborne reinforcements before they ever reached the Baltics. (See Map.)
Sitting astride of NATO’s most likely reinforcement route, Sweden could mitigate many of Russia’s military advantages. That is what makes Sweden so important to NATO. Were Sweden to allow NATO reinforcements to sail through its territorial waters, NATO could halve the distance over which its reinforcements would be exposed to Russian air and missile attacks between Denmark and Estonia. Theoretically, Stockholm could even allow NATO to safely transport its troops and supplies over land to Sweden’s east-coast ports before they embarked for an amphibious assault across the Baltic Sea.
Sweden also controls Gotland, an island situated in the middle of the Baltic Sea. Gotland is strategic because it is an ideal location from which to defend forces moving through the Baltic Sea or to project power into the Baltics. Though primarily seen today as a holiday destination, it has been prized for its strategic location for centuries. During the Cold War, Sweden stationed a reinforced armored brigade, fast attack craft, and a fighter squadron on Gotland to defend it. While all of those forces have since been deactivated or dispersed, Russia’s recent aggressive behavior prompted Sweden to reestablish a permanent military garrison on Gotland in 2016.
NATO also sees the value of Gotland. At a minimum, the island could complicate Russian anti-ship cruise missile strikes on NATO reinforcements sailing to the Baltics. But if Swedish cooperation with NATO were to increase, NATO air forces could use Gotland’s airfields to fend off Russian air and missile attacks as well as provide air support for NATO military operations in the Baltics. Gotland’s main port of Visby could even serve as a logistical hub for NATO forces fighting in the region.
On the other hand, Sweden could also help NATO by simply defending its territory from Russian incursions during a conflict between NATO and Russia. Doing so would constrain Russian freedom of action in the Baltic Sea. If nothing else, denying Russia use of Gotland would prevent it from not only making any seaborne reinforcement of the Baltics extremely difficult and thus narrowing NATO’s operational options, but also threatening the Baltic coasts of Germany and Poland behind NATO’s frontline.
Sweden in NATO?
Though not a member of NATO, Sweden is important to NATO’s defense of the Baltics.
Swedish cooperation with the Alliance would make protecting the Baltics easier and thereby strengthen NATO’s security guarantee to its member countries. That, in turn, would improve NATO’s ability to deter Russian aggression in the region.
Meanwhile, some have begun to speculate whether Sweden would shed its longtime “alliance-free” foreign policy and join NATO. But Swedish Foreign Minister Margot Wallstroem has dismissed such speculation. She cautioned that NATO membership “would expose Sweden to risks, both political and otherwise” which her government was not willing to bear.
Still, over the last decade, Sweden has taken a more active role in Nordic and European Union defense arrangements, many of whose members are also NATO members. Moreover, Sweden has stepped up its direct military contacts with NATO and the United States. While NATO membership may be off the table for Sweden, it would appear that Sweden has come to believe that NATO’s interest in deterring Russian aggression is very much in its own national interest, too.
 Damien Sharkov, “Putin Vows Military Response to ‘Eliminate NATO Threat’ If Sweden Joins U.S.-Led Alliance,” Newsweek, June 2, 2017, http://www.newsweek.com/vladimir-putin-vows-eliminate-nato-threat-sweden-joins-619486.