NATO’s eastern front is gearing up for Russian military exercises on its boundary, with Europe remaining highly vigilant following an unprecedented drone intrusion earlier this week.

The Kremlin will hold its sabre-rattling Zapad 2025 exercises with Belarus near Poland and Lithuania from Friday until next Tuesday, September 16.

These exercises typically occur approximately every four years. The last round in 2021 resulted in a significant force accumulation in Belarus, which was later used to launch an offensive against Ukraine.

A former NATO official cautioned that this year’s exercises could potentially act as a pretense for a military buildup, with tens of thousands of troops anticipated to participate.

Carsten Breuer, Germany’s defense chief, stated that NATO would remain watchful during the exercises, while NATO’s head, Mark Rutte, pointed out that Russia is rapidly strengthening its military capabilities.

Rutte warned that simultaneous offensives from Russia in Europe and China in Asia might spark World War Three, with Putin potentially diverting NATO’s attention through an attack in Europe.

The exercise, known as Zapad, signifies ‘West’ and is officially a defensive drill. According to official reports, troops will practice countering an assault, including air attacks and sabotage.

But Russia is expected to bring potentially tens of thousands of troops to rehearse, among other things, using its new nuclear-capable missile on Europe’s frontier.

Polish Prime Minister Donald Tusk closed the border with Belarus over the ‘very aggressive’ nuclear drills. Some will take place just a few miles from NATO borders.

Poland is still scrambling to respond to an incursion of 19 Russian drones that crossed over into its airspace overnight between Tuesday and Wednesday.

Tusk invoked Article 4 of the North Atlantic Treaty for the 8th time since NATO’s inception on Wednesday.

It serves as a starting point for major operations and will pave the way for consultations around the perceived threat to territory, independence or security.

The U.N. Security Council will also hold an emergency meeting at Poland’s request to discuss the drone incursion, the Polish Foreign Ministry said on Thursday.

Moscow denied responsibility for the incident, with a senior diplomat in Poland saying the drones had come from the direction of Ukraine, which Russia invaded in 2022.

Russia’s Defence Ministry said its drones had carried out a major attack on military facilities in western Ukraine, but it had not planned to hit any targets in Poland.

With the spectre of war looming over Europe, the Zapad drills come at a precarious time.

Zapad’s organisers say that their drills will not exceed 13,000 personnel, and Belarus has said it will be inviting observers from NATO countries this year.

The actual number of troops is likely to be far higher than 13,000, analysts have already warned.

The Zapad-2021 drills, a prelude to the war in Ukraine, was expected to host 12,800 servicemen; it ended up closer to 200,000, according to Russian authorities.

Satellite images provided by Planet Labs also indicate the construction of a potential military facility in Belarus, according to military analysts.

A site near Minsk, previously used to house Soviet nuclear weapons, appeared in late August to be under redevelopment.

Experts told RFE/RL that they could be used to store ‘strategic level equipment’, including – perhaps – the Oreshnik missile.

‘It is probably going to be nuclear-armed or it will probably be a nuclear component attached to it because they are using the facilities that were already used to house such…equipment during the Cold War,’ Konrad Muzyka, director of the security analysis firm Rochan Consulting, told the outlet.

Lieutenant General (Ret.) Lance Landrum, CEPA Fellow and Former Deputy Chair of NATO’s Military Committee said that this year’s exercise should be compared with the events leading up to the invasion of Ukraine in February 2022.

‘I do think it could serve as a cover. Now we have to look and see what exactly they do in this upcoming exercise, because we have a lot of historical intelligence on previous exercises, and we can compare that,’ he said.

Lt. Gen. Lance Landrum (Ret) added that there would be ‘a lot to be learned here’. For NATO, the drills will offer a window into Russian capabilities and strategies.

An absence of drone activity, crucial for both sides in the war in Ukraine, could indicate Russia lacks the personnel and equipment to train at scale after three-and-a-half years of war.

NATO may also glean insights about Russia’s capacity for electronic interference and jamming. 

Russian and Belarusian forces are expected to practice planning to use the new Russian Oreshnik nuclear-capable missile systems.

Russia’s intermediate-range ballistic missile was used in Ukraine’s Dnipro for the first time last year in what President Vladimir Putin called a ‘test’.

Oreshnik is expensive and makes little sense in Ukraine, where troops are often dispersed across a wide and open front line.

But it does pose a threat to compact targets like air bases – likely first targets in a war with NATO in Europe.

NATO said it will monitor Russia’s activity ‘very closely’, adding ‘we do not see any immediate military threat against any NATO ally’ but ‘we remain vigilant’.

The comment was published days before a drone incursion into Polish airspace overnight between Tuesday and Wednesday pushed tensions to a recent high.

Poland’s prime minister said that the country had identified ’19 violations and shot down at least three drones’, accusing Russia of a deliberate intrusion.

For its part, Russia denied the drones was Russian. The Kremlin said it was a matter for the defence ministry, and accused Warsaw of spreading ‘myths’ to escalate the war in Ukraine. It also offered to hold ‘consultations’ with its Polish equivalent.

Poland was resolute in its assessment. Donald Tusk said there was ‘no doubt that this provocation is incomparably more dangerous … than any previous ones’.

‘This situation brings us all closer to open conflict, closer than at any time since the Second World War,’ he said.

Poland subsequently invoked NATO’s Article 4, under which any member can call urgent talks when it feels its ‘territorial integrity, political independence or security’ are at risk.

The U.N. Security Council will also hold an emergency meeting at Poland’s request to discuss the matter, Poland said.

‘(We are) drawing the world’s attention to this unprecedented Russian drone attack on a member of the UN, EU, and NATO,’ Foreign Minister Radoslaw Sikorski told local radio.

‘I have appeared before the UN (Security) Council in the past, and it seems to me that our arguments have been convincing.’

The West is also holding its own military drills this month. It says the exercises are a ‘response’ to Zapad.

‘Poland will respond to the Zapad 2025 exercises … in an appropriate manner on the Polish side,’ Deputy Defense Minister Cezary Tomczyk told broadcaster RMF in April.

Iron-Defender-25 will see some 30,000 troops from Poland and NATO allied countries take part in exercises by land, air and sea in the Baltic region.

The drills ‘will jointly test their ability to deter and effectively defend the territory of Poland’, a press release from the Polish government says.

Poland’s Armed Forces General Command said the drills began on September 1, a day after the Russian-led Collective Security Treaty Organization drills began in Belarus.