Eight of the Baltic Sea states are now in NATO, and just one littoral country, Russia, is not. That might seem a mismatch of force — the so-called NATO lake — but appearances can be deceptive, and no one should underestimate the ability of Moscow’s military to bring a serious fight to the “flooded meadow” of the wider Baltic region.

Russian land-based aircraft and missiles, medium and small combat ships, and Kilo-class submarines have the potential to seriously disrupt the flow of vital supplies to Latvia, Lithuania, Estonia, and Finland, nations hemmed in by the Baltic and the territory of Russia and its Belarusian ally.

Sweden has now become the lynchpin of the northern NATO supply network through the vital port of Gothenburg, which lies at the junction of the Skagerrak and Kattegat straits, through which all shipping must pass between the Baltic and the North Sea.

At the same time, Stockholm’s forces are moving from a strategy of stopping invaders at its border to a more expeditionary role in support of wider NATO requirements (Swedish troops are now stationed in Latvia, for example).

But regardless of NATO’s new members creating a new strategic geography, there is no doubt that it will be a hard fight in the event of war with Russia.

The Russian Baltic Fleet may be the smallest of Russia’s main fleets, but it boasts a number of new surface combatants, along with other warships, land-based aircraft and missiles, and significant mine-laying capacity. There are fewer Russian submarines in the Baltic than at any time in the recent past, but as the full-scale invasion of Ukraine showed, Moscow can quickly reinforce any of its fleets if needed.

The Baltic region is also a joint battlespace with relatively short weapon ranges that would allow rapid Russian action if its missile systems fully live up to expectations.

The Russian line of navigation through the Baltic to St. Petersburg, currently served by a shadow fleet of tankers avoiding sanctions on oil and gas exports, is as important to Moscow as allied resupply is to NATO, and the Russians would certainly fight to defend it.