Russia has previously been invaded by France and Germany, and it would seem pretty obvious that it is going to react when the Ukraine starts making noises about joining the EU. At times I wonder if the EU was being naive or deliberately provocative.
Interesting point. Cameron, that well-known Europhile, went to Kazakhstan last year and expressed his wish to see an EU spreading from the Atlantic to the Urals. The EU then courted Ukraine only for the then elected Ukrainian PM to veto the deal. This is when it all kicked off and we had the unedifying view of Ashton and Van Rompuy in the Ukraine lending their support to the demonstrators who eventually overthrew the elected leader. OK he was a corrupt bugger but they only had to wait a few months for the next election to come round, the problem here of course being that the East would have probably voted for him to stay in power.
Is it any wonder that Putin reacted by moving in to the Crimea and allowing the people a vote to leave the Ukraine. Consequently we see no fighting in the Crimea and doubtless this situation would be replicated in E Ukraine if the people there were given a vote too. Having goaded Putin into action these sanctimonious words and this bellicose finger pointing from Cameron are laughable.
Putin was right over Syria too. Remember that Cameron was all for going in with all guns blazing and lending support to the so-called rebels against Assad. Fortunately wiser heads in Parliament voted this one down. These very Al Qaeda and ISIS factions are now running amok throughout the Middle East.
I think the truth is that few on any of the sides you mentioned are particularly nice people with decent motives. It's hard to see Putin as a victim in all of this. As ever, it's ordinary people who suffer.