Sweden’s governing Social Democratic Party announced on Sunday that it would vote in favor of joining NATO, all but guaranteeing that the Nordic nation would end 200 years of neutrality and seek membership in the powerful Western military alliance.
“We Social Democrats believe the best for Sweden and the Swedish people’s security is to join NATO,” Prime Minister Magdalena Andersson said in a news conference in Stockholm on Sunday evening.
“Military nonalignment has served Sweden well, but our conclusion is that it won’t serve us equally well in the future,” she added. “This is not a decision to be taken lightly.”
The Social Democratic Party, Sweden’s largest party and head of a minority coalition, has supported Swedish neutrality since before the collapse of the Soviet Union and favored Swedish military nonalignment even after Stockholm joined the European Union.
But Russia’s invasion of Ukraine has shifted public opinion significantly, in part because neighboring Finland — long a strategic partner of Sweden’s — has also moved swiftly to drop nonalignment and favor joining NATO.
Both countries have been shaken by the Russian invasion and have judged that close cooperation with NATO, without membership, did not include the guarantee of collective security that the alliance provides.
As late as March 8, two weeks after the invasion began, Ms. Andersson, Sweden’s Social Democratic leader, said that her party was opposed to joining NATO. But lawmakers were pulled along by Finland and shifting public opinion, along with a degree of anguish and discussions with party members in all 26 districts in the country.
Its announcement should guarantee a broad majority in Sweden’s Parliament because much of the political opposition is already in favor of applying for NATO membership.
Sweden is scheduled to hold a parliamentary debate on Monday, the same day as Finland.
Some Swedish parties continue to oppose joining NATO, arguing that membership brings heavy obligations as well as guarantees, and would narrow or even foreclose Sweden’s ability to choose when and how to act in the world.
There is also anxiety about Sweden, long a proponent of nuclear disarmament, joining a nuclear alliance, although some member states, including Norway, have opted out of hosting any nuclear weapons or foreign bases.
Both Sweden’s Left Party and the Greens will vote against membership while condemning Russia’s invasion, arguing that Sweden should improve its own defenses and maintain military nonalignment, which has kept the country out of war since 1814.
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Ali Esbati, a legislator for the Left Party, said that joining NATO carried new risks for Sweden’s security. “We want to keep our freedom to decide what conflicts we want to get involved in,” he said, “and it’s not clear that being part of a military alliance with a nuclear doctrine makes Sweden safer.”
Throwing aside a 200-year-old doctrine now seems wrong, Mr. Esbati added. “The whole process has been bizarrely forced,” with no parliamentary debate.
“It would be reasonable to put this to an electoral test, if not an election, then a referendum,” he said.
Marta Stenevi of the Greens said she worried about the authoritarian nature of some current NATO members, like Turkey and Hungary.
“We want to actively participate in the crises we choose,” Ms. Stenevi said. “To keep a strong voice for peace and democracy is easier outside the alliance.” But if Sweden joins, she added, “we need a much broader discussion of how we continue to work for our values.”
Both Sweden and Finland have been promised bilateral security assistance from the United States and Britain in the interim before full membership, a process that could take six months to a year.