Sweden and Finland have traditionally operated their own military alliance, choosing neutrality rather than the obligations of NATO.

But public opinion has shifted, particularly in Finland, and despite warnings from Russia and threats of repercussions both countries look set this year to choose the benefits of membership.

Finland shares a 1,300-kilometer border with Russia, and before war in Ukraine was content to make its own arrangements with Moscow.

But today that land border stands quiet. Economic trade has been frozen by sanctions, and relations with the Kremlin are cooling fast.

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Finland's Foreign Minister Pekka Haavisto says the Finnish public has swung in favour of joining NATO. "The government adopted tis kind of NATO option that things should be reassessed if the security situation changes," he said in a recent interview.

"And of course, we are in the middle of very dramatic change."

The Finnish and Swedish armies often train together; two close neighbors, both outside NATO. But like their respective governments, the soldiers on the ground are taking a view on the new Russia.

Major Stefan Nordstrom of the Swedish army says Russia's military action is unacceptable. "We would be naïve not to recognise that there is a threat," he says.

Every year NATO troops from across the alliance train together, rehearsing scenarios and standardizing tactics.

Whether it's U.S. Marines training with Norwegian troops in the Arctic Circle, or Italian infantry and artillery units going through live firing drills in the Latvian countryside, supported by U.S. Apache helicopters – it's all NATO.

From Alaska to Turkey, 30 member states are obliged and ready to defend each other at a moment's notice – as Article 5 of the treaty requires.

In 2004 seven new states joined NATO, former Soviet countries turning their backs on Moscow. NATO's growth is perceived by the Kremlin as a challenge, if not a threat.

"There have been multiple rounds of NATO enlargement, and it's not necessarily because of the threat from Russia that countries want to join," says Rachel Rizzo of the Atlantic Council. "It's because of the protections and the other benefits of being part of NATO, what that brings a country."

And now, since February, that NATO community is closer than ever, military spending looks set to rise, and member governments will be keen to announce new additions at an important summit in June.

"I expect that after the conference, we will see increased defense spending," says Kenton White from Reading University. "We will see increased numbers of troops on high readiness."

As well as the sophistication of the Swedish and Finnish armed forces, the addition of Finland would double the length of the NATO border with Russia.

If this goes ahead it will be a direct result of Russia's actions in Ukraine – the Kremlin's policies serving to strengthen the very alliance it wants to undermine.