Turkish lawmakers approved Finland’s application to join NATO on Thursday, making it the 31st member of the transatlantic alliance.

“All 30 NATO members have now ratified Finland’s membership,” Finnish President Sauli Niinistö said on March 30, per the Washington Examiner. “I want to thank every one of them for their trust and support. Finland will be a strong and capable ally, committed to the security of the alliance.”

Each member country must ratify the entry of a new nation into the alliance. Turkey had been holding out on its acceptance of both Finland and Sweden on the basis that they were too welcoming of groups Turkish President Recep Tayyip Erdogan claims are terrorists.

Erdogan’s administration has taken a strong stance against the Kurdish separatist movement, with Turkish troops and Kurdish groups like the PKK frequently clashing over these past few years.

Both Finland and Sweden instituted arms embargos on Turkey as retaliatory measures for its attacks on Kurds, but they have since repealed them to facilitate their NATO bids.

In fact, to resolve the dispute, the three countries negotiated a trilateral memorandum last June in which Finland and Sweden, as “prospective NATO Allies … extend their full support to Turkiye against threats to its national security.”

Russia’s invasion of Ukraine has played a significant role in both Nordic countries’ efforts to seek refuge under the NATO umbrella and abate Erdogan’s reservations.

Sweden still finds itself in the Turkish president’s crosshairs. Erdogan recently alleged that the country was embracing Kurdish terrorists and letting them organize rallies in its capital, per the BBC.

Hungary also opposes Sweden’s accession.

It claims that its representatives “have been repeatedly keen to bash Hungary through diplomatic means, using their political influence to harm Hungarian interests,” a spokesman for the Hungarian government, Zoltan Kovacs, said on March 29, per Reuters.

Hungary’s prime minister, Viktor Orban, has been criticized by Sweden as well as other member states of the European Union for allegedly eroding the rule of law since his rule began in 2010.

He has since breached democratic principles by filling the government with loyalists, writing a new constitution, and targeting minorities, according to his opponents, who froze Hungary’s access to the EU’s Cohesion Fund.

NATO Secretary-General Jens Stoltenberg told the press last week, “The most important thing is that both Finland and Sweden become members as soon as possible, not that they join exactly the same time. And we will continue to work hard. It will be a top priority to ensure that also Sweden will become a full member in the near future.”

For Finland, NATO membership marks a historic milestone.

“Finland is now ready to join NATO,” Niinistö said, per the Washington Examiner. “We look forward to welcoming Sweden to join us as soon as possible.”

Russia has promised retaliation against Finland and Sweden were they to join NATO, the extension of which it views as an existential threat.

The Russian ambassador to Sweden, Viktor Tatarintsev, issued a warning on the embassy’s website on March 28.

“If anyone still believes that this [NATO membership] in any way will somehow improve Europe’s security, you can be sure that the new members of the hostile bloc will become a legitimate target for Russian retaliatory measures, including military ones,” Tatarintsev wrote, per The Local.

NATO had already extended its protection to Sweden and Finland as applicants.

“Many allies have given security assurances to both Finland and Sweden,” Stoltenberg said last week, per the Washington Examiner. “So it is absolutely inconceivable that there will be any threat against Finland or Sweden without NATO reacting.”

Finland will be formally added to the NATO roster at the next summit in July.