There is Ukraine and there is Ukraine+NATO. In Russia's security interests, only the latter is worthy of war. Ukraine had a coup in 2014, installing an anti-Rus

There is Ukraine and there is Ukraine+NATO. In Russia's security interests, only the latter is worthy of war. Ukraine had a coup in 2014, installing an anti-Russian regime who then made overtures of joining with NATO (aka the US military cloaked in international "defensive" armor). This is why they responded in Crimea and now. This isn't happening in a vacuum.