- Sweden and Finland ended decades of military non-alignment in Europe and applied to join NATO.
- Their decision came after Russia's invasion of Ukraine.
- NATO Secretary General Jens Stoltenberg called it a "historic moment" and welcomed the applications.
Sweden and Finland formally applied to join the North Atlantic Treaty Organization, ending decades of neutrality and marking a massive shift in Europe's security landscape.
Finland and Sweden's ambassadors to NATO, Klaus Korhonen and Axel Wernhoff, handed in their applications to join the bloc to NATO Secretary General Jens Stoltenberg at the alliance's headquarters in Brussels on Wednesday morning.
NATO welcomed Sweden and Finland's application.
"This is a historic moment, which we must seize," Stoltenberg said Wednesday, Reuters reported.
"I warmly welcome requests by Finland and Sweden to join NATO. You are our closest partners, and your membership in NATO will increase our shared security."
Both countries, which stayed militarily non-aligned throughout the Cold War and beyond, made their decisions after Russia's invasion of Ukraine began. Finland shares a long border with Russia, and Sweden borders Finland.
The move would expand NATO's eastern borders significantly — a result that would likely anger Russian President Vladimir Putin and his officials, who have long complained about the alliance's eastward expansion and used it as a justification for invading Ukraine in late February.
Russia has also repeatedly threatened consequences against Finland and Sweden if they joined NATO.
Yet in a jarring reversal this week, Russian officials started downplaying the effect of the two nations joining NATO.
Putin said on Monday that Russia would have "no problem with these states" joining the bloc.
Russian Foreign Minister Sergei Lavrov also said on Tuesday that Finland and Sweden had already been "participating in NATO military exercises for many years."
Finland and Sweden's accession, which would boost NATO to 32 total members, could take several weeks or months.