15:58:
The press office for the Ukraine defence ministry in Crimea confirms to the BBC that an ultimatum from Russia’s Black Sea Fleet has been delivered. The Russian naval forces are said to have given Ukraine’s forces in the region until 05:00 local time (03:00 GMT) to surrender or else face an all-out assault.
The Russians are setting up an escalation. Not shooting but something like cutting off water and power to the Ukrainian bases.
What is there to assault in the Crimea? I think that Ukraine has one infantry brigade and no armor in that region, backed up by perhaps one squadron of aircraft. It's a pretty "safe" bet by the Russians as not much is going to challenge them.