The key to understanding Russian policy in the former Soviet Union is found in an interview Vladimir Putin gave back in 2003. Asked what his foreign policy was, he said something to the effect of "I aim to keep what's ours."
So much said, in so few words. All hail technique.
Thus, for example, what Russia sees as 'its' might include:
- any territories ever conquered by the Tsars or Stalin (including eg the three small Baltic republics, large chunks of Poland and Finland etc)
- any territories that belonged to the USSR
- any territories that belonged to the Russian SSR
- any territories where Russian influence 'naturally' belongs
- anywhere where non-trivial numbers of Russian citizens find themselves outside Russia's current borders (hence the busy policy of handing out Russian passports to Russian-speakers or others showing due fealty to Moscow, eg in Georgia/Abkhazia and now in Ukraine)