No press conference, no speech from a podium. Russia sent its sharpest message to NATO in an informal diplomatic document, delivered through the Russian embassy in Belgium. The content, however, is anything but informal: if the Alliance tries to cut the Kaliningrad region off from the rest of Russia, Moscow is ready to reach for everything it has.

"Russia is ready to use the entire arsenal of weapons at its disposal to defend its territory," the document says. In it, Moscow accuses the Alliance of an "unprecedented escalation of the military-political situation" around Kaliningrad and claims member states are already rehearsing what isolating it would look like. Such a development, according to Russia, "would significantly increase the risk of a direct armed clash."

The reply from Brussels came quickly and followed a familiar script. "I can confirm that Russia sent NATO an informal document and that we have responded," said NATO spokesperson Allison Hart. The Alliance is defensive, its exercises "pose no risk to any part of Russia," and Hart added: "We strongly condemn the threat of the use of force, including any irresponsible nuclear rhetoric." NATO says it has the means to defend its members' territory.

Why Kaliningrad

Kaliningrad is a Russian exclave on the Baltic Sea, completely cut off from the mainland and wedged between Poland and Lithuania - both NATO members. It's home to the headquarters of Russia's Baltic Fleet, and Moscow has also deployed Iskander missile systems there, capable of carrying both conventional and nuclear warheads. In other words: a piece of Russia with nuclear teeth, surrounded by Alliance countries.

The tensions didn't come out of nowhere. On September 23, a Russian Mi-8 military helicopter briefly flew from the Kaliningrad region into Polish airspace, and Poland scrambled fighter jets. Last week, NATO aircraft repeatedly intercepted Russian military planes flying between Kaliningrad and the rest of Russia with their transponders off and no filed flight plans.

Moscow has claimed for some time that NATO is preparing scenarios to blockade the exclave, and the Alliance denies it. Both sides say they are only defending themselves - and that is exactly the sentence the most dangerous spirals begin with. The Balkans know that scene by heart.

This isn't some distant Baltic story. Article 5 of the collective defence treaty applies to all members, including Macedonia, which has been in the Alliance since 2020. The question is whether anyone in Brussels or Moscow is still counting how many steps are left between diplomatic paper and real fire.