Part of Ukraine's significance on the world stage is its location. Europe currently depends on Russia for about 40% of its natural gas, according to Jeffrey Mankoff, deputy director of the Russia and Eurasia program at the Center for Strategic and International Studies. About half of that supply flows through pipelines in Ukraine.
Ukraine's dependence is even higher – one of the terms of Russia's controversial deal with Kiev included steep discounts on natural gas. Russia has cut off that flow in past disputes with Ukraine; another disruption could push up energy prices for businesses and households.