There is some truth to that. But I think a sub can make its way through the Bosporos. Also, there’s Russian soil in the Black Sea and the Azomov Sea.
How deep is thee wter in the Bosporos? Does Turkey have any submarines? Do they have some kind of torpedos targeted into the Bosporos? How have they stopped passage of the Bosporos?
The Azov sea is only 30 feet deep, more or less. Not sub friendly at all. The only shipping channels have been dredged. The rest of the BlackSsea ain’t much for deep either And I doubt if a sub could re-arm at Sochi, a nice ski resort. That would leave ship-to-ship re-arming and that would create a target rich environment. Our Sat guys seem to be feeding the Ukes dope on ship locations so I pretty much expect Ivan’s navy is running out of “game.”