Turkey controls the Bosphorus Strait, the only entrance to the Black Sea — and a major thoroughfare for Russian shipping. A ship watcher and geopolitical analyst, Yoruk Isik, spent the weeks leading up to the invasion of Ukraine noting a high number of Russian warships passing through. Now that those are blocked from entry, he’ll keep an eye on Russian cargo ships and oil tankers, which are now selling crude at reduced prices to whomever will buy it.