AMNA NAWAZ: Today, Estonia formally accused Russia of an arson attack on a robotics company this past August that it said was staged by Moscow's Secret Services, part of a wave of Russian sabotage across Europe.

In Poland, leaders are warning that Russia is planning a major attack to test NATO.

The foreign minister tells the "News Hour" they have credible intelligence to back that up.

From Poland's border with Russia's Baltic enclave, Kaliningrad, Malcolm Brabant reports.

MALCOLM BRABANT: On the outer limits of NATO territory, a Border Patrol checks for breaches in the razor wire that separates the alliance from Vladimir Putin's Russia.

Ever since Russia's invasion of Ukraine, there's been a cold war here, but now it's heating up.

Five yards to my left over there, behind the razor wire is the Russian enclave of Kaliningrad, and, on this side, it's Poland and the European Union.

Now, things may seem extremely peaceful right now, but the sensitivities are such that we're not allowed to point our camera towards Russian territory.

And things are quite hot along this long border with Kaliningrad.

In the past day or so, there has been a Russian helicopter which has come across into Polish airspace.

Polish aircraft was scrambled to send it away.

And the Ministry of Defense in Warsaw said this was yet another example of Russia testing NATO's defenses.

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COL.

MIROSLAWA ALEKSANDROWICZ, Polish Border Guard (through translator): As far as the border is concerned, it is stable.

MALCOLM BRABANT: Lieutenant Colonel Miroslawa Aleksandrowicz is spokeswoman for the border force monitoring a 140-mile-long stretch of frontier.

LT.

COL.

MIROSLAWA ALEKSANDROWICZ (through translator): It is important for us that this is the external border of the European Union.

And we must be ready, prepared for protection, no matter what time of day it is, what day of the week it is.

MALCOLM BRABANT: Three miles from the border is the town of Bezledy, where residents aren't at all fazed by the escalating rhetoric.

MAN (through translator): With Russia, you know it's dangerous everywhere, but here in Bezledy, it's peaceful.

It's good.

MAN (through translator): It's safe here.

It's fine.

We have lived here our whole lives and it's cool.

MAN (through translator): We lived here so many years, so it's nothing special for us.

WOMAN (through translator): Sometimes, there's a moment when I think about war, and then I'm a bit scared.

But I try not to think about it, that it won't be like Ukraine.

MALCOLM BRABANT: But, yesterday, more Polish aircraft were scrambled as Russia launched a drone attack on Ukraine.

The Poles on high alert for a potential attack on their soil.

RADOSLAW SIKORSKI, Polish Foreign Minister: Well, we gather intelligence from all kinds of sources.

We have learned in this country for 500 years that, when the Russians threaten, you can trust them.

MALCOLM BRABANT: Radoslaw Sikorski is Poland's foreign minister.

RADOSLAW SIKORSKI: In Europe, we have incidents almost every day.

There are assassinations.

There are arsons.

There are attacks on critical infrastructure.

And there are drone and cruise missile incursions.

And there are strikes on border crossings with Romania, with Moldova, with Poland.

And the Russians seem to be preparing some kind of augmentation of this tactics.

Clearly, we don't know exactly what, because only one person knows.

MALCOLM BRABANT: And that person, of course, is President Vladimir Putin.

FILIP BRYJKA, Polish Institute of International Affairs: Russia is still trying to maintain some sort of plausible deniability despite the fact that it's totally uncredible.

MALCOLM BRABANT: Defense analyst Filip Bryjka is a specialist in hybrid warfare.

FILIP BRYJKA: In my personal overview, it's more than certain that Russia will intensify its sabotage campaign in Europe, but at the same time, we should be prepared for more drone and missile incursions, probably combined with disinformation psychological operations claiming that Russia is not responsible for that.

MALCOLM BRABANT: Earlier this month, Vladimir Putin responded to such fears with a poker face.

VLADIMIR PUTIN, Russian President (through translator): I have spoken already about some European leaders.

In order to justify their position and their excessive spending on the war in Ukraine, they are willing to use anything and everything.

In particular, one of their main arguments is the alleged threat from Russia.

I want to state once again Russia has no aggressive intentions towards Europe or European countries.

There are simply no grounds for this whatsoever.

We are ready for cooperation and for restoring relations with our European neighbors.

JACEK SIEWIERA, Former Head of Polish National Security Bureau: Question of how far is the war, war is around us.

MALCOLM BRABANT: Jacek Siewiera is the former head of Poland's National Security Bureau.

Do you think that Putin's playing games with NATO and Poland?

Is he just teasing you?

Or is he serious, do you think, about having a confrontation?

JACEK SIEWIERA: I'm absolutely sure that Putin is serious about confrontation, which should lead to Russian domination over the European part of NATO.

Putin is a realist about his capabilities to dominate entire NATO, but he believes that he can dominate European part of it, especially Central Europe, and, following that fact, also the Western Europe, because then the spirit of NATO already will be broken.

MALCOLM BRABANT: Poland's history of invasion and repression by the former Soviet Union makes it perhaps NATO's most strident critic of Russia.

It's building a military capable of backing up its rhetoric with action.

With 220,000 people in uniform, it has the biggest armed forces in the European Union.

The ferocity of yesterday's attack on Kyiv was another reminder of the drone threat to Ukraine's NATO neighbors, as Polish Prime Minister Donald Tusk told Parliament earlier this month.

DONALD TUSK, Polish Prime Minister (through translator): There is a real risk that drones or other types of projectiles will enter the territory of one or several countries on the eastern flank and even cause destruction, and the official narration will be that it's an accident, and there is no reason for NATO to think about a response.

MALCOLM BRABANT: And Poland's foreign minister issued a rallying cry to his NATO allies.

The message to Moscow is that the alliance will not be intimidated.

RADOSLAW SIKORSKI: Ukraine is a country with one-tenth of Russia's GDP, and yet Ukraine has been heroically and effectively resisting Russia and confounding Putin's plans.

Poland has half of Russia's GDP, so five times the challenge, Europe 10 times Russia's GDP, NATO 25 times Russia's GDP.

So Putin can still kill a lot of people, but he can't win.

MALCOLM BRABANT: The frontier with Kaliningrad is one of NATO's trip wires.

The profound hope here is that it remains this peaceful.

For the "PBS News Hour," I'm Malcolm Brabant on the Polish-Russian border.