Russia's invasion of Ukraine has pushed Finland and Sweden to the verge of applying for NATO membership and abandoning a belief held for decades that peace was best kept by not publicly choosing sides.
Finland, which shares a 1300km border with Russia, and Sweden are now seen as highly likely to join NATO, which Russia says would have "serious military and political consequences".
Here are some of the issues that have led to a radical rethink of policy and what the next steps could be toward entering the 30-nation, US-led alliance.
Why are Sweden and Finland not NATO members?
Both have been non-aligned since World War Two despite having small military forces, relative to Russia. Finland gained independence from Russia in 1917 and fought two wars against it during World War Two during which it lost some territory to Moscow.
Finland has relied on its own military deterrence and friendly relations with Moscow to keep the peace. But with Russia's invasion of Ukraine, which Moscow calls a "special operation", Russian President Vladimir Putin looks anything but friendly.
Sweden has not fought a war for 200 years (the Swedish-Norwegian war of 1814) and post-war foreign policy has focused on supporting democracy internationally, multilateral dialogue and nuclear disarmament. It ran down its military after the Cold War, hoping in the event of any conflict it could delay a Russian advance until help arrived. Mr Putin's offensive against Ukraine has made a guarantee of aid much more appealing. However, many on the left in Sweden remain suspicious of the US security agenda and NATO, which ultimately relies on the deterrence provided by the US nuclear arsenal.
Both Finland and Sweden switched from formal neutrality to military non-alignment in 1995 when they joined the European Union. They've drawn ever closer to NATO in recent years, exchanging intelligence and participating in alliance exercises, in response to an increasingly belligerent Russia.
Joining the alliance would bring Sweden and Finland under the umbrella of Article 5, which guarantees that an attack on one NATO ally is an attack on all.
How broad is support for NATO membership?
Polls show a slim majority of Swedes back joining NATO and there is a majority in parliament in support of an application. Sweden's Social Democrats - the biggest party and in power for most of the last century - are seen as the biggest hurdle to applying, though they are reviewing their objections. The Swedish Left Party - formerly the communist party - is against, as is the Green Party.
The most recent poll, by private Finnish broadcaster MTV, showed 68 per cent of Finns in favour and only 12 per cent against NATO membership. Media reports indicate a majority of Finnish lawmakers and most parties support joining NATO, with the exception of the Left Alliance.
When could they join?
Finland looks closer to applying for membership than Sweden. It has a NATO "option", a kind of a plan of action that mandates applying if the security situation deteriorates. Social Democrat Prime Minister Sanna Marin, who heads Finland's five-party centre-left coalition, and President Sauli Niinisto have been touring different NATO member countries in recent weeks securing support for a potential application.
Finland's government updated its foreign and security policy on Wednesday, stating that Russia's invasion of Ukraine had profoundly changed Finland's security environment but took no stance on whether or not Finland should join NATO. It will now be discussed by parliament, and Marin said a decision would be taken "within weeks, not months".
NATO holds a summit in Madrid in June.
Sweden's government is also reviewing broad security policy with a report due before the end of May. The ruling Social Democrats are holding an internal debate on whether to drop their objection to NATO and are expected to issue a report before summer.
Sweden holds a general election in September with NATO membership a central issue. A clear mandate from voters would make it easier for a government to apply.
However, a decision by Finland to apply before that would heap pressure on Stockholm to follow suit.
