At a simplistic level, Russia can be criticised for militarily intervening in Ukraine and violating its sovereignty and territorial integrity. But this does not take into account the train of events that led to this crisis. A broader perspective will enable a more objective view. The Ukraine issue has been simmering since the dissolution of the Soviet Union. President Putin is right when he characterised it as the biggest geopolitical disaster of the 20th century. A superpower armed with a formidable nuclear capability collapsed from within. The separation of Ukraine—the historical core of the Slavic Russian state and its Orthodox character—has been traumatic for Russia.
Tensions between Russia and Ukraine have been a reality over internal political conflicts within Ukraine, Russian oil supplies and pricing, ethnic, linguistic and religious differences between the western and eastern parts of the country, extremist right-wing Russia-hating nationalist elements in western Ukraine incorporated into the Soviet Union by Stalin, treatment of Russian-speaking ethnic minorities in eastern Ukraine, the push inside Ukraine to join the European Union and NATO, and so on. These came to a head in 2014 when street protests supported by the US in particular, as part of its agenda to promote colour revolutions, overthrew the legitimately-elected government of President Yanukovych over the issue of Ukraine accepting the EU offer of an Association Agreement (favoured by the protestors) and Russia’s counter-offer of joining the Eurasian Economic Union instead (favoured by the President).