Ukraine's defence ministry has been given orders to withdraw all its forces from Crimea, acting Ukrainian president Oleksander Turchinov has said.
Mr Turchinov said the decision was taken because of Russian military threats to lives and the health of Ukrainian servicemen and their families.
An unusually frank Nato Secretary General issued an unequivocal warning on the course of events should Russia attack Latvia or Estonia.
The West responds with sanctions and closer political ties with Ukraine as Russia's President seals the annexing of Crimea to much fanfare.
Supporters of the controversial fracking industry believe shale gas could be America's most potent weapon in the stand-off with Russia.