3/1: Russia approves military involvement in Ukraine; Obama tells Putin to step back

      |Thousands of Russian soldiers have arrived in Crimea, taking control of roads and Crimean air space. In response, Ukraine's armed forces were ordered to be at full readiness, and the country's acting prime minister warned that Russian military intervention would be the beginning of war; and, President Obama had a tense 90-minute conversation with Russian President Vladimir Putin, telling him that a military intervention is a clear violation of international law.

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