The Soviet Union Came Apart Along Ethnic Lines. The Most Important Factor In This Breakup Was The Disinclination Of Slavic Ukraine To Continue Under A Regime Dominated By Slavic Russia. Yugoslavia Came Apart Also, Beginning With A Brutal Clash Between Serbia And Croatia, Here Again 'nations' With Only The Smallest Differences In Genealogy; With, Indeed, Practically A Common Language. Ethnic Conflict Does Not Require Great Differences; Small Will Do.