The NATO alliance has signaled it will welcome both of the Nordic countries with open arms as it spreads north to deter Russian aggression.

This is the first time that a Prime Minister and President have confirmed that a country will apply for NATO. Niinisto told reporters that a new era begins.

The Prime Minister of Sweden said on Monday that her country wants to become a member of NATO.

There is a broad majority in the parliament for Sweden to join NATO.

All current NATO members have to agree on any decision on NATO expansion. Turkey's president said last week that he might block the two Nordic countries from joining because of their alleged support for Kurdish extremists. NATO Secretary General Jens Stoltenberg is confident that Turkey will address its concerns and that it won't derail its ambitions of joining the alliance.

Turkey has made it clear that they are not going to block membership, according to the Washington Post.

'Everything changed when Russia invaded Ukraine'

Ukraine soldier cigarette Kharkiv
A Ukrainian serviceman smokes a cigarette in a trench at the front line east of Kharkiv, March 31, 2022
FADEL SENNA / AFP) (Photo by FADEL SENNA/AFP via Getty Images

The historic development puts both countries on the verge of a dramatic break from a longstanding tradition of neutrality, and stands as one of the starkest examples of how the Ukraine war has backfired on Russian President Vladimir Putin.

The leader of the Russian Federation often complained of NATO&s long-standing eastward expansion in the lead-up to the invasion. Adding Sweden and Finland to NATO is sure to anger Moscow, which threatened to retaliate over the move.

In the past, Finland and Russia have gone to war over the border. The Winter War was fought between the Finns and Russians during World War II. Though it put up a strong fight against the Red Army, it was eventually defeated and lost 10% of its territory to the Soviet Union.

During the Cold War, Finland remained non-aligned.

The Soviets pledged not to invade again after signing a treaty with the Finns in 1948. Moscow had a lot of influence over the politics of Finns and its statehood was limited.

The term "Finlandization" would eventually be used by political scientists to describe the restricted form of statehood. In the lead-up to the Russian invasion of Ukraine in February, some suggested thatFinlandization was a potential model for Kyiv to accept in order to avert a broader conflict.

Sweden was neutral during the Cold War. Sweden has not been involved in a war for over a century. Sweden's neutrality has long been a topic of debate, particularly in relation to World War II. As the tide turned against the Germans, the Swedes allowed the Nazi army to transit its country and the Allies to use air bases.

Both countries became NATO partner countries after the fall of the Soviet Union. Before the invasion of Ukraine, neither Sweden nor Finland appeared to be interested in pursuing full NATO membership. At a joint press conference with her Swedish counterpart in Stockholm in April, the prime minister said everything changed when Russia invaded Ukraine.

The war in Ukraine resulted in dramatic changes in tone from both Sweden and Finland on the subject of NATO membership. After the invasion, polling in both countries showed growing public support for joining the alliance. If the Finn government decided to pursue NATO membership, the president told Russia to look at the mirror.

Russia has threatened to retaliate if Finland and Sweden join NATO

Russian President Vladimir Putin speaking with advisors.
Russian President Vladimir Putin attends the military parade during 77th anniversary of the Victory Day in Red Square in Moscow, Russia on May 9, 2022.
Sefa Karacan/Getty Images

The principle of collective defense is included in the founding treaty of NATO. An attack on one member is considered an attack on all. Following the 9/11 terror attacks in the US, article 5 was only used. NATO has conducted military operations in the past without being attacked first.

The alliance wants to avoid a direct confrontation with Russia and will not send troops to help it fight Russian forces. NATO refused to set up a no-fly zone in Ukraine because it would require alliance countries to shoot down Russian warplanes, which would amount to a declaration of war. NATO countries have poured military assistance into Ukraine, though they have avoided direct involvement in the war.

Before applying to NATO, Sweden and Finland broke from their traditions of neutrality to send weapons and other military aid to Ukraine.

Both Sweden and Finland have military assets that can be used for NATO.

The defense analyst for the Finns told Foreign Policy in April that the army is exceptional. When most other countries switched to crisis management using small units, that has been the focus of their training. The general staff officers are still trained to lead brigades.

Sweden has beefed up its navy in the Baltics in response to the growing threat posed by Russia.

Russia has threatened to retaliate against both countries for pursuing NATO membership. Russia has suffered huge troop losses due to the war in Ukraine. The ability of Moscow to take military action against countries that have the backing of an alliance with several nuclear powers is limited.

In an interview with Insider in April, the pro-NATO former prime minister said he expected Russia to retaliate with a cyberattack.

Baker contributed reporting.