The US, the EU and NATO intervened in Ukraine, which resulted in civil war. Russia had nothing to do with it.
“Since the interference and subversion of the USA, the EU and NATO, a precarious civil war takes place in the country which, at the same time, is the driving force of an impending war against Russia… The ‘Ukrainian democracy movement’, the “Maidan”, was a chimera, an invention cooked up in the poisonous kitchens of the Western secret services”.
The Office of the Prosecutor of the International Criminal Court has stated that "the information available suggests that the situation within the territory of Crimea and Sevastopol amounts to an international armed conflict between Ukraine and the Russian Federation". This international armed conflict began at the latest on 26 February when the Russian Federation deployed members of its armed forces to gain control over parts of the Ukrainian territory without the consent of the Ukrainian government.
The European Union stated in July 2014 that "arms and fighters continue flowing into Ukraine from the Russian Federation".
According to the US Defense Intelligence Agency (DIA), Russian special forces and troops operated to mobilize, lead, equip, and support separatist militias in the Donbass region in Eastern Ukraine from spring 2014 to the present, although their presence was denied by Moscow.
Russian President Vladimir Putin admitted Russia's military presence in Ukraine in 2015.