Following the 2014 Ukrainian revolution in March 2014, the Russian Federation annexed Crimea. According to Putin this was done because "Crimea has always been and remains an inseparable part of Russia". After the Russian annexion of Crimea he said that Ukraine includes "regions of Russia's historic south" and "was created on a whim by the Bolsheviks". He went on to declare that the February 2014 ousting of Ukrainian President Viktor Yanukovych had been orchestrated by the West as an attempt to weaken Russia. "Our Western partners have crossed a line. They behaved rudely, irresponsibly and unprofessionally," he said, adding that the people who had come to power in Ukraine were "nationalists, neo-Nazis, Russophobes and anti-Semites". In a July 2014 speech midst an armed insurgency in Eastern Ukraine Putin stated he would use Russia's "entire arsenal" and "the right of self defence" to protect Russian speakers outside Russia.
Source: Wikipedia