The threat seemingly appears during every Ukraine crisis.
In 2004, governors in eastern Ukraine warned that Russia-friendly regions in the east would split if Viktor Yushchenko became president. The disputed election of Viktor Yanukovych, a Russia-backed candidate, was overturned and Yushchenko won in a revote. The country remained politically divided, but discussion of eastern secession quickly withered.
Ten years later, Yanukovych, elected in 2010 after disappointment in the 2004 Orange Revolution, has been ousted, and the east-west divide has again come to the fore. Iterations of maps like this one, shown on Al Jazeera on the day Yanukovych fled Kiev, have told the story thusly.
The eastern part of the country, stretching from Kharkiv Oblast, to the border regions of Donetsk and Luhansk and to the Crimean Peninsula, is seen as predominantly Russian. Indeed, major cities in the east are largely Russian-speaking industrial hubs and the autonomous Crimean Republic is overwhelmingly Russian-speaking.
But a closer look within oblasts like Kharkiv shows that maps like the one above may oversimplify the divide. Kharkiv Oblast includes Kharkiv, Ukraine's second-largest city. Its governor, Mykhaylo Dobkin, recently led a conference of pro-Russian governors that rejected the authority of Ukraine's new government and the region voted strongly for Yanukovych's Party of Regions in the 2010 presidential election.