In response to Russia’s invasion of Ukraine, Sweden and Finland, two long-standing militarily non-aligned countries, are now likely to join NATO. Public opinion in both countries had been mostly against joining the Western military alliance, but the war in Ukraine has dramatically changed attitudes. Leaders of both countries have said a formal application to join could be submitted soon, with the prospect of membership by the summer. Of course, Russia does not like this. Dmitry Medvedev, deputy chairman of Russia’s Security Council, threatened to deploy Russian nuclear weapons in the Baltic region if Sweden and Finland joined. There would be “no more talk of any nuclear-free status for the Baltic – the balance must be restored,” he said. Ironically, it is precisely this language, coupled with the aggression in Ukraine, that has convinced many in Sweden and Finland to consider joining NATO after years of hesitancy. Things began to change in 2014 after Russia’s annexation of Crimea. At the NATO summit in Wales that year, the allies created a new category of engagement called “enhanced opportunity” partners to deepencooperation with non-NATO countries. Finland and Sweden are now two of the five such partners. Both have participated in NATO-led operations over the years, without being members. Swedish and Finnish troops are part of NATO’s mission in Kosovo, and contributed to the International Security Assistance Force in Afghanistan. Sweden also joined NATO’s operation in Libya in 2011. Both countries maintain a military capability that exceeds most existing NATO members. Furthermore, as theyare both Arctic nations, they can address the growing importance and challenges of the Arctic and rectify the glaring need for NATO to draw up an Arctic strategy. Both countries are critical for NATO’s ability to defend and, if necessary, retake the Baltic states in the event ofRussian aggression. Militarily speaking, the three Baltic states — Estonia, Latvia, and Lithuania — are isolated from other NATO members. It would be extremely difficult for NATO to respond to an incident in the Baltic without the acquiescence of Finland and Sweden. History has shown that most military operations in the Baltic region require access to Swedish and Finnish air, sea, and land. For example, during the Crimean War (1853–1856) and the Allied intervention in the Russian Civil War (1918–1920), the Swedish fortress of Viapori (today known as Suomenlinna in Finland) played a crucial role. During both world wars, the Skagerrak and Oresund Straits — both of which border Swedish waters and are a gateway to the Baltic Sea — were highly contested. History has shown that most military operations in the Baltic region require access to Swedish and Finnish air, sea, and land. Luke Coffey Two places in particular are crucial to the region’s security. The first are the Alands, a group of Finnish islandswhere the primary spoken language is Swedish. They have always been considered the most important geostrategic piece of real estate in the Baltic Sea. Since the 1856 Treaty of Paris, which ended the Crimean War, the Aland Islands have been demilitarized. For the victors this was considered a major achievement of the war. British Prime Minister Lord Palmerston told the House of Commons in 1856 that demilitarization of the islands “placed a barrier between Russia and the north of Europe.” While the islands are demilitarized, in the event of an armed conflict with Russia in the region they would be fought over. The second is Gotland Island in Sweden, strategically located halfway between Sweden and Latvia in the middle of the Baltic Sea. Sweden maintained a permanent military garrison there for hundreds of years until 2005. Due to increased tensions with Russia in the Baltic Sea, the Swedish government has once again bulked up defenses on the island. Swedish and Finnish NATO membership would greatly contribute to the overall security of the alliance. NATO enlargement has helped bind like-minded democracies on both sides of the Atlantic in mutual self-defense. Considering the military capabilities possessed by Finland and Sweden, their geographic location in the Baltic Sea, and their close relationship with the three Baltic states, it would make sense for NATO to welcome them. NATO membership would make Sweden and Finland safer too. With Russia’s invasion of Ukraine, the geopolitical landscape in Europe has changed in a way not seen since the Second World War, so membership should be enthusiastically supported by the alliance. Russia may not like Sweden and Finland joining, but it does not have a say. Ultimately, the Swedish and Finnish populations will decide. In the meantime the alliance should make it clear that the door is open. Luke Coffey is the director of the Douglas and Sarah Allison Center for Foreign Policy at the Heritage Foundation. Twitter: @LukeDCoffey