Going through the Black Sea straights will get a lot more difficult when Saudi Arabia and Iran start fighting each other. Watch oil prices escalate...AGAIN!
https://www.eia.gov/todayinenergy/detail.php?id=26352
Actuality, the choke point between them is the Straights of Hormuz at the Persian Gulf.
Iran has set up a forward war base in Syria with their best generals. Trump is not going to allow a land bridge to the hezzies...