Finland said on Thursday it would apply to join NATO "without delay", with Sweden expected to follow suit, suggesting Russia's invasion of Ukraine will bring about the very expansion of the Western military alliance that Vladimir Putin aimed to prevent.
The decision by the two Nordic countries to abandon the neutrality they maintained throughout the Cold War would be one of the biggest shifts in European security in decades. Finland's announcement drew fury from the Kremlin, which called it a direct threat to Russia and threatened an unspecified response, news agency Reuters reported today.
It came even as Russia's war in Ukraine was hitting another turning point, with Ukrainian forces driving Russian troops out of the region around the second largest city Kharkiv, their fastest advance since forcing Russia to withdraw from the capital and northeast more than a month ago.
NATO Secretary-General Jens Stoltenberg said the Finns would be "warmly welcomed" and promised an accession process that would be "smooth and swift". Finnish membership would boost both Finland's security and that of the alliance, he said.
Finland and Sweden are the two biggest EU countries that had yet to join NATO, and Finland's 1,300-km (800-mile) border will more than double the frontier between the U.S.-led alliance and Russia, putting NATO guards a few hours' drive from the northern outskirts of St Petersburg.
"Finland must apply for NATO membership without delay," President Sauli Niinisto and Prime Minister Sanna Marin said in a joint statement. "We hope that the national steps still needed to make this decision will be taken rapidly within the next few days."
Asked whether Finland's accession to NATO posed a direct threat to Russia, Kremlin spokesman Dmitry Peskov said: "Definitely. NATO expansion does not make our continent more stable and secure.
"This cannot fail to arouse our regret, and is a reason for corresponding symmetrical responses on our side," he added, without specifying the possible responses. Russian officials have spoken in the past about measures including potentially stationing nuclear-armed missiles on the Baltic Sea.
Asked on Wednesday if Finland would provoke Russia by joining NATO, Niinisto said: "My response would be that (Putin)caused this. Look at the mirror."
Five diplomats and officials told Reuters that NATO allies expect both countries to be granted membership quickly, paving the way for an increased troop presence in the Nordic region to defend them during a one-year ratification period.
Putin cited NATO's potential expansion as one of the main reasons for Moscow's "special military operation" in Ukraine he launched in February. Ukraine has long sought to join NATO, although it has lately offered to accept some form of neutral status as part of peace talks.
NATO describes itself as a defensive alliance, built around a treaty declaring that an attack on one member is an attack on all, which effectively grants U.S. allies the protection of American superpower might, including its nuclear arsenal.
Moscow regards that as a threat to its influence in neighbouring countries. But Putin's decision to invade Ukraine has caused a shift in public opinion in the Nordic region, with political parties that had backed neutrality for generations now coming to embrace the view that Russia is a menace.
On the front lines, Ukraine has mounted a bold counter-offensive in recent days that has ousted Russian forces from villages north and east of Kharkiv, where Russian troops had held the outskirts since the beginning of the invasion.
Reuters journalists have confirmed in recent days that Ukraine is now in control of territory on the banks of the Siverskiy Donets River, around 40 km (25 miles) from Kharkiv.
To the north, the Ukrainians have been pushing towards the Russian border. In the latest advance, they announced on Wednesday the recapture of the village of Pytomnyk, halfway to the Russian frontier along the main highway north of Kharkiv.
"The withdrawal of Russian forces from the Kharkiv Oblast (region) is a tacit recognition of Russia’s inability to capture key Ukrainian cities where they expected limited resistance from the population," Britain's defence ministry said in an update on Thursday.
Ukraine's general staff said in an update overnight that the Russians were regrouping "in order to prevent our forces from advancing further" around Kharkiv, with combat under way where Russian troops had crossed the Siverskiy Donets.
Ukraine's advances near Kharkiv could put some of Russia's main supply lines to eastern Ukraine, located on the far bank of the river, within range of Ukrainian artillery, and even allow it to bombard staging areas inside Russia.
Both sides reported strikes overnight across the Russia-Ukraine border, which Reuters was not able to confirm.
Ukrainian officials reported shelling across the frontier from the Russian border town of Tyotkino, and air strikes that killed and wounded civilians in the northern Ukrainian city of Novhorod-Siversky. Russia said one person was killed and seven wounded in Solokhi, a village in the Belgorod border region.
Elsewhere, the Ukraine general staff said Russia had had some success advancing towards Kudryashivka and Sievierodonetsk, part of Moscow's main assault in the eastern Donbas region.
Air strikes were continuing on Azovstal, a giant steelworks in the ruined southeastern port city of Mariupol where Ukrainian defenders have been making a last stand.
In the hamlet of Vilkhivka on Kharkiv's eastern outskirts, the Ukrainian advance had made it possible for residents to return to comb through the wreckage of homes destroyed in heavy fighting weeks ago.
A grizzled pensioner recounted how Russian troops had used him and other villagers as human shields before retreating after fierce fighting.
“Can they really be called real soldiers after that?” he spat. “They are motherfuckers, not military men!”