It was, perhaps, the highest praise ever offered by one intelligence agency to another – and it was certainly the most British.

As chief of MI6 in 2022, Sir Richard Moore publicly declared that “pound for pound”, the “brilliant” Estonian Foreign Intelligence Service (EFIS) “probably knock us into a cocked hat”.

Kaupo Rosin, the director general of that service, is delighted by the compliment, though he asks with polite bewilderment what this expression about cocked hats could possibly mean.

“It’s always good to see that our partners value us and our activities,” he says, after I offer assurances that Moore’s phrase was a great tribute. “But I have to say the same about the British services who are top-notch, with world-leading, excellent capabilities, and are doing an incredible job.”

I meet Rosin at EFIS headquarters in Estonia’s capital, Tallinn, where it could hardly be more necessary for intelligence officers to do incredible jobs. Russia is only 130 miles away – the border is a two-hour drive down what was known in Soviet times as the M11 highway. Vladimir Putin’s home city of St Petersburg, meanwhile, is four hours away.

No country understands the dangers of being a neighbour of Russia more acutely than Estonia, which endured five decades of Soviet, then Nazi and then, again, Soviet occupation before regaining its independence in 1991. The nation has been reborn as an increasingly prosperous democracy with, since 2004, membership of both Nato and the EU.

Yet Putin’s burning ambition to re-establish the Russian empire casts a long shadow. Estonia is the smallest of the three Baltic states, both in population (1.3 million) and land area (17,500 square miles, just over half the size of Scotland), and it has the longest border with Russia (180 miles). That perilous combination means that if Putin were to seek a new target after – or perhaps during – his onslaught against Ukraine, then Estonia could be in his crosshairs, and there have been plenty of warnings recently about the possibility of a Russian attack on Nato.

If the Russians were to strike across the border, then Britain, too, would be at war. Estonia is a Nato ally and 1,000 British troops lead a multinational battlegroup in the country, amounting to the Army’s biggest overseas deployment.

Rosin and his spies must do everything humanly possible to understand Russian intentions and capabilities for the simple reason that the very survival of their homeland may depend upon it. Their special insight and expertise on Russia is what earned them the public praise of MI6.

Perhaps for that reason, Rosin believes that we should abandon euphemisms like “hybrid warfare”, and call Putin’s escalating campaign of sabotage and subversion across Europe by its proper name of “state-sponsored terrorism”.

‘Putin, at this point, only has bad options’

Since Rosin’s service is superbly informed on developments inside Russia, I begin by asking how Putin and his circle view their blood-soaked predicament in Ukraine. “What he expresses or emanates is that victory for Russia will come at one point – and that we just have to continue and keep going. But I’m not sure if people around Putin are as convinced as he might be,” replies Rosin.

“There are certainly voices which express that he should keep going, but I think the voices which, let’s say, urge [him] to maybe reconsider the situation are becoming stronger and stronger.”

Rosin adds: “What he has, at this point, are only bad options. And each decision he makes has different risks for him. So the decision to continue has the risk that with the heavy losses and the economic situation, the internal problems and tensions in Russia mount.

“That might have, at some point in the future, an impact on his political future, if people around him come to the conclusion… that it is better to continue without him.

“But if he stops, that has the risk for him that he will be shown as a weak person. So there is really something for him to think about at this point. But I think, objectively, Russia is in a very bad place at the moment, and many people understand this in Russia, especially people in the economic field, and probably some of the oligarchs already. So I’m sure they have serious discussions.”

‘More Russians do not want this war’

Rosin, 48, is tall, burly and uses carefully considered English. Like most intelligence chiefs, he speaks in public, but sparingly – this is his first set-piece interview with a British newspaper – and only the bare bones of his previous career are disclosed. Family life is not something that spies discuss with journalists.

Rosin fixes me with a firm gaze through partially rimless glasses. As he talks about Russia – and uses the word “objectively” – he reminds me of a quizzical and dispassionate doctor describing the condition of a particularly troublesome patient.

Rosin provides a list of Russia’s Putin-inflicted ailments. “The losses on the battlefield exceed the recruitment numbers,” he says. “The economy has taken a serious hit. One of the reasons is the Ukrainian long-range strikes against oil infrastructure, which is the main income for the Russian budget. There are huge financial problems already. The budget deficit has already exceeded the planned deficit for this year, and it will be, we assess, maybe around 10 trillion rubles [£86bn], which is half of the defence budget.”

Putin would normally cover a deficit of that size without difficulty, except that sanctions have largely excluded Russia from the biggest financial markets, making it far harder and more expensive for the Kremlin to borrow.

“The question is, ‘How do they mitigate that issue?'” asks Rosin. “Probably tax increases, asking oligarchs for contributions, and companies for contributions to the state budget, which, let’s say, creates an additional reason for internal discontent and internal pressure.”

Rosin continues: “We see that overall unhappiness levels with this war are increasing in all echelons of society, starting from normal people and throughout, up to the oligarchs. More and more people do not want this war. The question is: what impact does this have on his [Putin’s] decision-making?”

Rosin is candid that he cannot answer that question, prompting me to wonder out loud whether the level of discontent might reach a level where Putin’s grip on power could be threatened.

“I do not see a street revolution happening at this point,” says Rosin. “More important is what people who have access to money, weapons and information – what do they think? In these circles, there is no more talk about total victory. People are discussing different scenarios, and mainly how to end this [war] in a proper way.”

Rosin adds: “But I would say, if something changes in Russia, then it will happen in a very rapid manner and we will all be surprised. It will be an overnight thing, if it ever happens.”

‘Mobilisation is coming’

Just how swiftly change could occur is shown by the sudden and abortive rebellion against Putin led by Yevgeny Prigozhin, the mercenary commander, in June 2023, when a column of mutineers advanced to within a 90-minute drive of the Kremlin.

“For us, it was a sign of how hollow the system might be inside – and that’s often the case in such regimes. They look very hard from outside, but inside they might be surprisingly weak,” says Rosin.

If Putin decides to ignore the voices of caution and persevere with his onslaught against Ukraine, he will have to find a way of replacing his battlefield losses, which total about 500,000 Russian dead, according to GCHQ, the British intelligence service. His only option could be to order a mobilisation and press-gang hundreds of thousands more Russians into service.

Putin has always been viscerally reluctant to take this step, fearing both popular discontent and the economic consequences of depriving the workforce of masses of able-bodied males. But he was compelled to resort to a partial mobilisation in September 2022 after Ukraine’s successful counter-offensive against his invasion.

Since then, he has doggedly avoided any repetition. Yet there is now mounting speculation that Putin will order another mobilisation, perhaps next month, once Russia’s sham parliamentary election is out of the way.

I ask Rosin whether he expects a Russian mobilisation. “What we see is that in Russian society, by now, everybody ‘knows’ that the mobilisation will come,” he answers. “There is a lot of talk about it in Russia. Everybody knows somebody who works in the military who has said that mobilisation will come.”

He adds: “This can have an effect where society somehow makes peace with this idea, and that would be for the Kremlin another incentive, then maybe to do it.”

On balance of probability, I ask, will Putin mobilise next month or not? “At this point, it’s an equal chance,” says Rosin. “Everybody thinks it’s coming. The system is ready. We haven’t seen any decision.”

A clash with Nato

Another danger that many believe is coming – particularly if Putin mobilises hundreds of thousands more troops – is a Russian attack on a Nato ally, possibly Estonia or another Baltic state.

I meet Rosin soon after the surprise visit to Moscow by John Ratcliffe, the CIA director, reportedly to warn the Kremlin against testing the alliance.

Rosin declines to say what he believes his American counterpart told the Russians, though he obliquely confirms that deterring aggression against Nato was at least part of the message.

I quote a report in the Wall Street Journal that Ratcliffe’s purpose was to “deliver a warning to Russia not to attack Nato countries”. Is that correct?

“I think that’s a bit exaggerated and there were other topics discussed, but I cannot really comment on other countries’ foreign relations,” replies Rosin carefully.

Did the CIA director discuss Nato and deterrence? Rosin again comes up quickly against the limits of what a spy can say. “It’s very hard for me to comment,” he agonises, before settling on an acceptable form of words: “I’m sure that his visit did not weaken deterrence.”

Later, the New York Times reports that Ratcliffe delivered a message strikingly similar to Rosin’s assessment that the Kremlin should understand the severity of Russia’s strategic and economic predicament.

For now, Rosin’s considered view is that Nato is continuing to deter Putin, and that Article V, the alliance’s mutual defence clause, remains credible, despite Donald Trump openly questioning whether America would defend its allies.

“I think, at this point, Putin understands that Article V is actually still valid. So we don’t see a near-term threat,” says Rosin.

The future lies in the West’s hands

Rosin spells out exactly what he means. For the next “one year-plus”, he does not expect Russia to launch a conventional military assault on a Nato ally. “The question is rather what does the future look like? Where are we in the West in one year, two years, five years from now, and if deterrence still works?” he adds.

The answer, says Rosin, is largely in the West’s own hands. If European countries press on with backing Ukraine and increasing defence spending while keeping America inside Nato, then Putin should continue to be deterred.

“If we take the Russia threat seriously, continue to invest in our defence, maintain a credible deterrence posture and have credible resourced defence plans, then we are able to deter Russia, yes,” he says.

But he enters a vital caveat. “If we ourselves in the West somehow screw it up, then this would create a new situation for Russia to recalculate, perhaps,” adds Rosin. “So it heavily depends on our activities, our investments and our seriousness.”

Estonia’s own seriousness is demonstrated by its defence spending of 3.4 per cent of GDP last year, according to Nato, well above Britain’s 2.4 per cent and even the US’s 3.2 per cent. A country with a population little bigger than Birmingham’s could deploy 80,000 trained reserve soldiers within days of any emergency (the trained strength of the British Army, by comparison, is 71,000).

‘Russian sabotage is becoming more violent’

Everything about EFIS conveys the deadly seriousness of its work. The location of its headquarters in Tallinn is not secret, but nor is it advertised. The building reveals itself to a visitor like – and this may be an insensitive metaphor – a Russian matryoshka doll.

From the street outside, you see nothing except a high wall shielding an anonymous office block with no sign or nameplate. Once through the perimeter entrance, the building begins to hint at its true purpose when you encounter three flagpoles – two flying the blue, black and white of Estonia, and one displaying the yellow and blue of Ukraine.

You notice that all its windows are hidden by screens. Then, safely behind the front door, the organisation finally declares itself. A large white sign displays the lion of Estonia and the word “Valisluureamet“, the Estonian name for EFIS.

In British terms, EFIS is MI6 and GCHQ combined, collecting both human and signals intelligence.

Rosin, a professional intelligence officer, has been in charge since November 2022. He began his career as a 19-year-old recruit in the Estonian army in 1996, completing a tour with the American-led coalition in Iraq in 2005, before rising to command military intelligence between 2012 and 2018.

He then spent four years with Nato’s Intelligence and Security Division at alliance headquarters in Brussels. He returned to Estonia in 2022 to take charge of all military cyber operations, and was soon promoted to lead EFIS.

As we talk, young and casually dressed intelligence officers are arriving for the working day. Rosin is clear that one of their biggest tasks is foiling the Kremlin’s ever-expanding campaign of sabotage and subversion across Europe.

The latest incident was at Leipzig-Halle airport in Germany on August 4 where an armed drone slammed into a Ukrainian Antonov cargo plane on the tarmac. Only the chance failure of the drone’s bomb to explode avoided the giant aircraft going up in flames at an airport used by two million passengers every year.

“It’s almost everywhere by now. It’s a campaign orchestrated by the Russian government through the GRU [Russian Military Intelligence] mainly,” says Rosin. “It is becoming more violent and dangerous. We see that the main targets, currently, are defence industry production sites, but also logistical sites.”

Russia’s goal, he adds, is to “disrupt European supplies, European weapons equipment deliveries to Ukraine”.

In Britain, for example, five men have been jailed for burning down two London warehouses in 2024 where supplies for Ukraine were being stored. Earlier this month, the Russian Embassy responded furiously to reports that Britain was supplying Ukraine with drones for long-range strikes deep inside Russia and openly threatened “consequences”.

Rosin is politely scornful of how “hybrid warfare” has become the catch-all term for these attacks. “Hybrid schmybrid,” he says derisively, adding that “hybrid” is a “nice and cosy word” that “distorts from the reality”, which is “sabotage, unconventional activities, cyber attacks and information warfare. This is what it actually is”.

Rosin adds: “Especially in the sabotage campaign, we could also use the term ‘state-sponsored terrorism’ because this is what it technically is.”

I mention the Leipzig-Halle airport attack. “It could be classified as terrorism, I would say. It’s a civilian target,” he says.

So far, he adds, “We in the West have been relatively successful in disrupting this – that’s a matter for intelligence services and counter-intelligence services. This is our work.”

And, so far, Russia’s campaign has failed to weaken Europe’s resolve to support Ukraine. But EFIS and dozens of allied intelligence services are waging a constant – and largely covert – effort to protect their respective countries.

Rosin’s EFIS might have earned the plaudits of MI6, yet the price of living in peace and freedom just down the road from Russia is eternal vigilance.