It's about as subtle as a brick, Russian forces have seized all of the important buildings in Crimea the fibre optic cable between Crimea and Kiev has been cut. Ukrainian forces in Crimea have been disarmed the Ukrainian naval headquarters is surrounded and Russian troops are digging in on the border between Crimea and the rest of Ukraine.
As johndrew stated, it is almost exactly what the Germans did in 1938 in annexing the Sudetenland on a pretext of protecting Sudeten Germans, and we all know how that little border incursion ended up, don't we?
Putin is playing for high stakes, he is banking on the west doing much harrumphing and bluster but basically doing nothing. He is gambling that we will let Ukraine go the same way as Georgia.
He had better hope we won't get involved militarily, because if we do, here comes WW3.