TurkStream, a two-line natural-gas pipeline running across the Black Sea from Russia.
After other routes closed, it became the sole remaining pipeline carrying Russian gas to Europe, delivering 31.5 billion cubic meters a year.
When Ukraine's gas-transit deal expired in January 2025, TurkStream was left as the only route: one line feeds Turkey, the second delivers to Europe via Bulgaria, which puts Turkey in the middle as a key energy gatekeeper but also ties it to Moscow, still Turkey's largest gas supplier.
It hands Turkey real power over Europe's remaining Russian gas while deepening its dependence on Russia. That two-way grip makes the pipeline a strategic pressure point.