Already picking fights with Russia in the Baltic Sea, and deploying ever growing numbers of ground troops in Eastern Europe, NATO’s latest focus in needling Russia is a major increase in naval presence in the Black Sea.

It makes sense from the position of NATO hawks. After all, the Black Sea includes one of Russia’s most historically important ports, at Sevastopol, and NATO is eager to contest Russia’s ownership of the Crimean Peninsula, in which that port is located.

It’s not going to be simple, however, as the effort will mostly have to come without the direct involvement of either the United States or Britain, NATO’s two biggest navies, and the two nations most eager to stick it to Russia.

That’s because the Montreaux Convention of 1936 strictly regulates the entry of warships from nations without coastal territory in the Black Sea, restricting the size of such ships entering the sea, and allowing those ships to only stay for 21 days.

This means that in practice Turkey is going to have to do the heavy lifting in building a Black Sea fleet, with Bulgaria and Romania the only two other NATO nations with any coast on the Black Sea. That limits their existing fleet strength, as all together the three nations only have a couple dozen frigates and some smaller ships. Russia’s Black Sea Fleet isn’t dramatically large either, but the Russian Navy overall is, and the nation will likely redeploy more ships into the sea as NATO escalates.