The gist is, Montreux Convention ensures free travel through the straits at peacetime but allows for restrictions at wartime. Wartime could be a war that involves the countries with a shore on the Black sea but not Turkey or a war where Turkey is involved too.
So the news is, Turkey took its time to decide if this is a War or a limited time military operation and come to conclusion that this is a war indeed. As a result Turkey activated the passage restrictions for military ships at a wartime where Turkey is not taking part in. This essentially means, the Russian(an other Black sea nations) ships that are based in the Black sea can get through but Turkey may restrict those based elsewhere. It also means that Turkey can restrict American and other 3rd party warships from passing through the Bosphorus.
The purpose of the Montreux Convention is to keep peace in the Black sea by allowing free movement at peacetime(Turks can't stop ships from passing, therefore no reason to take it away from Turkey with force) and predefined restrictions at wartime(Turks can stop ships that are not based there, therefore limit the military build up), so this is not necessarily a pro-Russian or pro-Ukrainian move.
Turkey sees the Montreux Convention as a primary mean to keep Turkey neutral in conflicts involving Russia and Istanbul out of the interests of large powers.
So the news is, Turkey took its time to decide if this is a War or a limited time military operation and come to conclusion that this is a war indeed. As a result Turkey activated the passage restrictions for military ships at a wartime where Turkey is not taking part in. This essentially means, the Russian(an other Black sea nations) ships that are based in the Black sea can get through but Turkey may restrict those based elsewhere. It also means that Turkey can restrict American and other 3rd party warships from passing through the Bosphorus.
The purpose of the Montreux Convention is to keep peace in the Black sea by allowing free movement at peacetime(Turks can't stop ships from passing, therefore no reason to take it away from Turkey with force) and predefined restrictions at wartime(Turks can stop ships that are not based there, therefore limit the military build up), so this is not necessarily a pro-Russian or pro-Ukrainian move.
Turkey sees the Montreux Convention as a primary mean to keep Turkey neutral in conflicts involving Russia and Istanbul out of the interests of large powers.