Why Did Vladimir Putin Invade Ukraine?

Those who believe Putin is trying to reestablish Russia as a great power say that once he gains control over Ukraine, he will turn his focus to other former Soviet republics, including the Baltic countries of Estonia, Latvia, and Lithuania, and eventually Bulgaria, Romania and even Poland.
“The Eurasian Empire will be constructed on the fundamental principle of the common enemy: the rejection of Atlanticism, the strategic control of the USA, and the refusal to allow liberal values to dominate us.” — Aleksandr Dugin, Russian strategist, “Foundation of Geopolitics: The Geopolitical Future of Russia.”