That means war because Russia will never consent to that.
Erdogan is the consummate geopolitical pot-stirrer.
He’s just running his mouth, as is his usual way.
The Turks are always entertaining.
Russia annexed Crimea in 2014–unopposed. The Obama/Biden Administration did very little in response.
Crimea is as much a part of Russia as Moscow. It will never be returned to Ukraine voluntarily. The overwhelming Russian-speaking population of Ukraine voted about 90% in a plebiscite to rejoin Russia.