The Russian embassy in London has put out a message with no diplomatic trimmings: any military attempt by Britain or NATO to attack or blockade the Kaliningrad region will be met "with all the means at Russia's disposal, including nuclear weapons." According to Moscow, it wouldn't be a local incident but an attack on the territory of the Russian Federation - with consequences for the whole Alliance.

"Those who advocate plans to blockade or attack Kaliningrad should not delude themselves about the possible consequences," the embassy said. In the same breath, Moscow repeated that it isn't seeking military confrontation with NATO and has no intention of attacking European countries - but that it will respond if the Alliance moves against Russian territory first. The reassurance about peace and the nuclear threat sit in the same statement, two lines apart.

Why Kaliningrad? A glance at the map is enough. The Russian exclave is wedged between Poland and Lithuania, two NATO members, and has no land link to the rest of Russia without crossing someone else's territory. It hosts part of the Baltic Fleet, missile systems and air defences. The land strip between Kaliningrad and Belarus, known as the Suwałki Gap, runs between Poland and Lithuania and has for years been seen as one of the most sensitive points on NATO's eastern flank.

The tensions didn't start yesterday. Back in May, the Russian Foreign Ministry claimed NATO was using military activity to work out scenarios for isolating the region. A particularly sharp reaction followed remarks by Lithuanian Foreign Minister Kęstutis Budrys, who said NATO had the means, in case of conflict, to destroy Russia's air and missile defence bases in Kaliningrad and "break through" Russian defences there. Moscow presented that as proof that the West is thinking about direct strikes on Russian territory. NATO officials, for their part, have not announced any decision on a blockade.

Putin had been even more direct. "Such actions would simply lead to an unprecedented escalation of the conflict, take it to a completely different level and expand it into a major armed conflict," he warned at the time. And asked about the statements from Lithuania, he answered more sharply still: "The Russian Federation has all the means to raze to the ground anyone who tries to do that."

What's new in this story is one sentence. Until now, the message was that a blockade would trigger a Russian military response. Now the embassy has explicitly mentioned nuclear weapons too. When a nuclear threat becomes a standard paragraph in a diplomatic statement, does the world still read it as a threat - or already as routine?

The Balkans know how quickly a strip of land, a corridor or a road between two states stops being a point on the map and becomes the pretext for something much bigger. Kaliningrad is exactly that kind of point - only this time there are nuclear arsenals on the table, not rifles.