Ukraine's warming to the ways of the west makes Russia nervous. Access to the black sea is a strategic issue. Reservoirs in Crimea drying up because their source is in Ukraine proper. I don't defend any of this aggression in the least, but if mexico and Canada started warming up to China, you could imagine how the US would react. Once again, I don't support or defend Russia in this situation, but at the same time I don't think it's the work of a madman.