Katya Adler

And how long have you worked here?

And how long have you worked here?

I mean, you must have seen it change a lot. We're just walking over the bridge between us here and... Until the middle. Until the middle. We're not going to walk right... You're not going to let us over into Russia, but... It's not the best idea, I think. No. Does Russia feel like a different neighbour now?

I mean, you must have seen it change a lot. We're just walking over the bridge between us here and... Until the middle. Until the middle. We're not going to walk right... You're not going to let us over into Russia, but... It's not the best idea, I think. No. Does Russia feel like a different neighbour now?

Does that worry you as a border guard?

Does that worry you as a border guard?

This is no ordinary plane ride. I'm on a very loud NATO surveillance plane, a 707, with a huge mushroom-looking radar on top of the aircraft. We're flying over the Baltic states. As I walk down the aisle, instead of rows of seats, I'm looking at rows of desks with NATO personnel scanning computer screens, searching for suspicious activity below by Russia.

This is no ordinary plane ride. I'm on a very loud NATO surveillance plane, a 707, with a huge mushroom-looking radar on top of the aircraft. We're flying over the Baltic states. As I walk down the aisle, instead of rows of seats, I'm looking at rows of desks with NATO personnel scanning computer screens, searching for suspicious activity below by Russia.

So NATO's showing its presence and they're showing theirs? Exactly. I can see Estonia clearly below us. It's policing missions like this and NATO membership, full stop, that for a long time has made the Baltics feel safe.

So NATO's showing its presence and they're showing theirs? Exactly. I can see Estonia clearly below us. It's policing missions like this and NATO membership, full stop, that for a long time has made the Baltics feel safe.

But Donald Trump is changing that with his far more open attitude towards Moscow and his very clear message for Europe that US military backing can no longer be taken for granted. That sent a chill through NATO members in the Baltics. I'm in the northern town of Narva by the river of the same name, dividing Estonia from Russia.

But Donald Trump is changing that with his far more open attitude towards Moscow and his very clear message for Europe that US military backing can no longer be taken for granted. That sent a chill through NATO members in the Baltics. I'm in the northern town of Narva by the river of the same name, dividing Estonia from Russia.

There's a medieval-looking fortress either side of the river, one flying the Russian, the other the Estonian flag. And in between, the bridge, one of Europe's last pedestrian crossings, still open to Russia. I've come to speak to border police chief Egert Belichev. Estonia's security services say Moscow is constantly testing them.

There's a medieval-looking fortress either side of the river, one flying the Russian, the other the Estonian flag. And in between, the bridge, one of Europe's last pedestrian crossings, still open to Russia. I've come to speak to border police chief Egert Belichev. Estonia's security services say Moscow is constantly testing them.

I'm coming out of the customs area where the border police are, back into the driving snow and past a huge queue of shivering people, many of them with cases, waiting to cross over into Russia. Excuse me, how long are you going to Russia for? I'm going for two weeks.

I'm coming out of the customs area where the border police are, back into the driving snow and past a huge queue of shivering people, many of them with cases, waiting to cross over into Russia. Excuse me, how long are you going to Russia for? I'm going for two weeks.

A whopping 96% of people in this part of Estonia are mother tongue Russian speakers. And Estonia worries that a confident Vladimir Putin could use this big ethnic Russian community here as an excuse to invade. It's a playbook he's used before in Georgia and Ukraine. Would NATO allies risk war with nuclear power Russia to defend this tiny corner of tiny Estonia?

A whopping 96% of people in this part of Estonia are mother tongue Russian speakers. And Estonia worries that a confident Vladimir Putin could use this big ethnic Russian community here as an excuse to invade. It's a playbook he's used before in Georgia and Ukraine. Would NATO allies risk war with nuclear power Russia to defend this tiny corner of tiny Estonia?

It's a question for Estonia's defence minister, Hanno Pevko.

It's a question for Estonia's defence minister, Hanno Pevko.