A prolonged crisis in Ukraine began on 21 November 2013, when then-president Viktor Yanukovych suspended preparations for the implementation of an association agreement with the European Union. This decision resulted in mass protests by its proponents, known as the "Euromaidan". After months of such protests, Yanukovych was ousted by the protesters on 22 February 2014, when he fled the Ukrainian capital city of Kiev. Following his ousting, unrest enveloped the largely Russophone eastern and southern regions of Ukraine, from where he had drawn most of his support. An ensuing political crisis and Russian military intervention in the Ukrainian autonomous region of Crimea resulted in the annexation of Crimea by Russia on 18 March 2014. Subsequently, unrest in Donetsk and Luhansk oblasts of Ukraine evolved into a war between the post-revolutionary Ukrainian government and pro-Russian insurgents, supported and often assisted by the Russian military and special forces.