have eyes on this Swedish island.

Once inhabited by Vikings

and as early as the eighth century,

this piece of land is of strategic importance.

That's because it's located in the center

of the Baltic Sea and is on NATO's European front line.

But it's also the only waterway

where Russia has direct access to the west.

Gotland is just one small part of how NATO could benefit

if Sweden and Finland become members of the block.

Both nations have said they will take steps

to apply for membership of the Western military alliance.

- But it is a very significant shift.

These are two countries that have sought

to take position of military non-alignment.

- Finish and Swedish membership in NATO

would greatly enhance the defense of the Baltic region

and reduce the chances of Russian adventurism

or attack across the air, land, and sea domains

in an integrated fashion.

- [Narrator] Analysts say the expansion

of the block could make NATO stronger

and affect Russia's current strategy in Ukraine.

To understand how, we need to look at the geography

and military capabilities of both countries.

The location of both Sweden and Finland

would mean the Alliance has significantly more land

in the east of Europe.

Take Finland, for example.

It has an 830-mile long border with Russia

but if we look a little closer,

we can see that this border is full of lakes

and marshland with very few roads

for military vehicles such as tanks to travel on.

Analysts say those conditions would be beneficial

for NATO in any potential combat situation with Russia.

- From a NATO point of view, it's a huge opportunity.

So you think about combat and Ukraine over by Kyiv,

where Russia was trying to push down really narrow roads.

That's Finland.

- [Narrator] One key area for Russia is the Kola Peninsula

where Moscow houses sub-launched ballistic missiles

that are key to its nuclear arsenal.

Currently, the only NATO country bordering the zone

is Norway, but analysts say if Finland joins the block,

it would increase pressure on the region.

- So suddenly, if Finland's having an exercise up here,

it's not just Norwegian forces,

you know, maybe a brigade or two,

now suddenly, it might be 50,000 troops.

So again, Russia has to now divert troops up there.

- [Narrator] In Sweden, Gotland is strategic for Russia

because it could be a base to protect its naval forces

in the Baltic Sea.

- And they would use that as a base of operations

for amphibious assault, for land attack,

for air attack and for naval attack.

- [Narrator] In 2017, NATO and Sweden worked together

on a simulated mission of a Baltic Sea attack

which Alberque said concluded the island

would be a central part of any invading strategy.

(missile blasting)

Although Finland and Sweden have been close NATO partners

for decades and worked on such joint missions,

they have remained militarily non-aligned.

For centuries, Sweden has largely avoided involvement

in military conflicts while Finland stayed out of NATO

after the Alliance formed in 1949,

largely to avoid provoking Russia.

- So the fact that they are deciding now

to potentially join the Alliance,

I think, is very significant and speaks to the sense

of vulnerability that countries feel

in the wake of Russia's invasion of Ukraine.

- [Narrator] Russia's invasions of Georgia in 2008

and Crimea in 2014 sounded alarm bells in both nations

but the current war pushed them

to reconsider NATO membership.

In response, Russia, which has long stood against

any eastward expansion of the block has issued threats.

According to the Kremlin,

Russian President Vladimir Putin told the Finish president

that ending the country's decades-long

non-aligned defense policy would be a mistake for Helsinki.

And Russian Deputy Foreign Minister Alexander Grushko

said that Moscow would need to take

adequate precautionary measures

if NATO were to deploy infrastructure

for nuclear weapons near Russia's borders,

including in Finland.

- I think one of the reasons that we saw the invasion

of Ukraine is because they are not a member of NATO

and that, you know, Russia felt that they could,

therefore, take the action they did

without incurring a direct response from NATO.

And so I think that is something that will be playing

into Moscow's of strategic calculus

that once these states are, if they become members of NATO,

then it will have to take a more indirect action.

- [Narrator] The addition of Finland and Sweden to NATO

would also enhance some of the block shortfalls

in air defense, according to Alberque.

- They do not have sufficient

vehicle-mounted air defense systems.

NATO air defenses, especially in the east

are very, very weak, and again,

this is a huge capability shortfall

that NATO's attempting to address.

- [Narrator] Sweden's advanced purchases

of air-launched cruise missiles

and Finland's $9.4 billion purchase

of 64 cutting edge US F-35 fighter jets

would significantly improve NATO's air defense

and attack capabilities.

And it could require Russia to add countermeasures

to that potential threat, analysts say,

spreading its resources thin

while trying to establish air dominance.

But some analysts also believe

that the introduction of Sweden and Finland

into the block could fit into a broader plan

by Russian President Vladimir Putin

to realign his forces to different regions.

- I think Russia thought a long time ago

that Finland and Sweden would end up joining NATO.

I think it helps Putin in terms of his messaging

that NATO is scary so that he can divert resources

from human development in Russia towards military.