At the end of September, a Telegram channel known for its network of Russian intelligence sources reported that a Black Sea fleet submarine had run into “serious technical problems” while on a mission off Gibraltar, in the Mediterranean. The Novorossiysk submarine was at risk of exploding, it said, and according to online sleuths, later surfaced, giving away its location. But the question remains, what was a Russian sub even doing there? This is what we know so far: