With many issues straining U.S. relations with Russia, one of the most contentious centers around the country of Ukraine. This eastern European nation, the second largest in Europe, shares a border with Russia and only gained its independence from the former Soviet Union in 1991. But a nearly four-year conflict in Ukraine between the government and pro-Russian separatists has claimed 10,000 lives and inflamed tensions between the U.S. and Russia not seen since the Cold War. Last month U.S. Secretary of State Rex Tillerson called the situation in Ukraine the single most difficult obstacle to establishing normal relations with Russia. NewsHour Weekend Special Correspondent Christopher Livesay went there to find out why.