Many comparisons have been made between the situation in Ukraine in 2014 and the outbreak of war in Yugoslavia in 1991, i.e.
Russia = Serbia (and Montenegro)
Ukraine = Croatia
Some rough figures to give you an idea of the relative scale:
Population of Russia = approx. 143 million
Population of Serbia and Montenegro = approx. 11 million
In other words, Russia has about 11 times the population.
Population of Ukraine = approx. 45 million
Population of Croatia = approx. 4.5 million
In other words, Ukraine has about 10 times the population.
So this war has the potential to be on 10 or 11 times the scale of the Serbian-Croatian conflict.
Also worth remembering: Ukraine has about the same population as Spain. So far the conflicts in the European ex-Soviet Union have taken place in much smaller countries (Georgia, Armenia, Azerbaijan, Moldova).
History repeats itself: the first time as tragedy, the second time as tragedy.