Russia has begun what it calls a partial withdrawal of forces from its eastern border with Ukraine. Around 500 troops are said to have pulled back so far. The build-up of Russian forces has emerged as a key point of contention between Russia and NATO countries in the aftermath of last month’s annexation of Crimea. NATO countries are meeting in Brussels today to discuss additional measures in response to the standoff with Russia, including joint military exercises between Ukrainian and U.S. forces.