Ukraine’s language divide:
From the Washington Post, “It's not just that Ukraine has two halves that predominantly speak different languages. They have different politics – and different visions for their country. Check out this composite of four maps: the top two show the language and ethnic divide, the bottom two show the election results for the 2004 and 2010 presidential elections. The lines are identical! (The Russian-speaking, eastern half of Ukraine tends to be, big surprise, more pro-Russian. Yanukovych is from that part of the country, has most of his support there, and did not even speak Ukrainian until he was in his 50s.)”
Top left: Ukraine's Russian-speakers in blue. Top right: Major ethnic and linguistic groups. Bottom left: 2004 presidential election results. Bottom right: 2010 presidential results. The western half of the country voted overwhelmingly against Yanukovcyh; that's also where, until very recently, most of the protests have been. Source: Washington Post, “9 questions about Ukraine you were too embarrassed to ask”
Original locations of Russian military in the Crimea.
Recent movements of same.
Location of gas pipelines through Ukraine to paying customers in Europe.
The imbalance in power, population … and gas.
And finally, as Bernard Darnton notes, “Like most unfixable conflicts, the dividing line is on an ancient map”: