This question has shot into prominence owing to increased intervention of Russia in Ukraine and its help to Syrian leadership last year in evicting the Islamic States.
Both these instances can be a seen as a display of strength by Russia in general and Vladimir Putin in particular to reflect a stronger side of Russia. This will enable it to showcase to the world that Russia is inching towards its pre-1992 stage when Russia was the Soviet Union indeed.
President Vladimir Putin has never kept secret of his ambition to restore the Russian power to the world and it is in fact his dream to make Russia a bigger entity in the world politics by igniting the flame of uniting all former partners of Soviet Union and inching them to become Soviet Union once again.

Though it is a reality that none of the former Soviet Union states have offered any rebellion to the interests of Vladimir Putin, Ukraine has responded in an aggressive manner.
Invasion of Crimea by Russia was a strategic move by Russia to convey a hard-hitting message to Ukraine that they should not offer rebellion to move being planned by Russia.
It still remains to be seen though if Vladimir Putin will be able to implement his strategies and move towards the goal of a united Soviet Union.