Finland and Sweden are expected to announce this week whether to apply to join NATO following Russia's Ukraine invasion, in what would be a stunning reversal of decades-long non-alignment policies.
The Nordic nations have been rattled by Moscow's war against its pro-Western neighbour, which has bolstered domestic support for joining the military alliance -- and the security that membership would provide.
"It is 100 percent certain that Finland will apply, and quite likely that it will be a member by the end of the year", researcher Charly Salonius-Pasternak of the Finnish Institute of International Affairs told AFP, with a majority in parliament backing membership.
Russia's February 24 invasion of Ukraine has also led to a swift turnaround in Finnish and Swedish public opinion in favour of NATO membership, which until recently had little backing.
A poll published Monday by Finnish public broadcaster Yle showed that a record 76 percent of Finns now support joining the alliance, up from the steady 20 to 30 percent registered in recent years.
Public opinion has also surged in Sweden, albeit to lower levels, with around half of Swedes now in favour.
After weeks of intense political meetings at home and abroad, all signs now point to the two countries announcing a joint bid before the end of the week.
Sweden's ruling Social Democratic Party said Monday it would announce its position on the NATO issue on May 15. A favourable stance would provide a clear parliamentary majority for an application.
Elisabeth Braw, an expert on Nordic countries' defence at the American Enterprise Institute, told AFP that even though Stockholm appears more hesitant than Helsinki, she believes the two countries "will do the application at the same time".
Traditionally accustomed to lengthy consensus-building debates on major issues, Sweden has been caught off-guard by Finland's swift turnaround.
"The Social Democrats in Sweden have always said: 'We'll think about this when Finland joins'... because they thought Finland would never join", Braw said.
- 'Perfect timing' -
Any NATO enlargement is bound to spark anger from Moscow, which has historically pushed back at any eastward expansion of the alliance and has strongly condemned any notions of Ukraine joining.
But Moscow's mounting warnings about the "political and military" consequences appear only to have strengthened Finland's and Sweden's resolve.
If Finland and Sweden do opt to join NATO, it will be in direct response to Moscow's military aggression in Ukraine.
And the alliance would move in right next door. Finnish membership would double NATO's land border with Russia to around 2,600 kilometres (1,615 miles).
And if they do join, the timing could be advantageous for Sweden and Finland.
"From a risk perspective, the timing is perfect", Braw said. "Russia is so busy elsewhere, it would be very hard for Russia to respond militarily."
In Finland, President Sauli Niinisto is expected to announce his "personal" opinion on the NATO question on Thursday, while Prime Minister Sanna Marin's Social Democratic Party is due to announce its decision by Saturday at the latest.
According to Finnish daily Iltalehti, a committee made up of the president, prime minister and four other cabinet ministers is to meet Sunday to make the country's final decision.
Asked by AFP, the Finnish government refused to comment on the report, saying the committee's meeting dates were confidential information.
- Exercises -
On Sweden's strategically-located Baltic Sea island of Gotland, Home Guard troops were last week called in for a special month-long training exercise, coinciding with annual military exercises taking place across Finland and Sweden next week.
With a professional army of 12,000, another 21,000 conscripts per year and a wartime force of 280,000 troops -- in addition to powerful artillery and around 60 fighter jets -- Finland's military might is impressive for a country of just 5.5 million people.
And while the post-Cold War period was marked by deep cuts in defence spending, Sweden also has a modern army that already meets NATO standards, as well as a cutting-edge arms industry.
During the Cold War, Finland remained neutral in exchange for guarantees from Moscow that it would not invade. Sweden meanwhile has long maintained a policy of neutrality during conflicts, dating back to the Napoleonic wars.
And while the two countries have until now chosen to remain outside NATO, they have gradually inched closer to the alliance over the years, taking part in its Partnership for Peace Program and NATO-led peacekeeping missions.
"It is a huge shift in public opinion and in the political decision. But militarily it wouldn't be, simply because they are already closely linked to NATO," Shaw said.
"They will marry NATO after having cohabited with NATO".