It's my hope that war doesn't start over there and a peaceful resolution can be found. It's true we have no exact idea where this military group came from that took over the military bases in Crimea, but they are way too organized and well equipped not to be a nations military. A band of citizen militia would looks something like this -
https://www.youtube.com/watch?v=ZJQW_0utHKY (you don't need sound, just fast forward to 57 seconds)
in Crimea we have these "pro-Russian" troops
https://www.youtube.com/watch?v=BdcHCJy9el8 (you don't need sound for this either)
Now if you compare these two groups you start to notice something. The second group has uniform uniforms and uniform weapons. Oh yeah and access to military grade vehicles. Those tend to get a bit expensive even for our rich elite. If you watch other videos such as how they took over a naval base, it shows a highly organized group of people coming into the building. Hardly the discipline of a ad-hoc citizen force. All this shows without a shadow of a doubt that a nation is involved.