For those who have been following the events in Ukraine, the reasons for Russia’s intervention are pretty clear, but they also point to what is likely to occur in the future.
Russia has always seen Ukraine as part of Russia. Henry Kissinger wrote an op-ed for the Washington Post: “Russian history began in what was called Kievan-Rus. The Russian religion spread from there. Ukraine has been part of Russia for centuries, and their histories were intertwined before then. Some of the most important battles for Russian freedom, starting with the Battle of Poltava in 1709, were fought on Ukrainian soil.” This doesn’t excuse Russian action, but it is important in understanding them.
STRATFOR has an excellent article on the geopolitics of the region. Geopolitics doesn’t explain or predict all foreign affairs but it is a very helpful theory in understanding the international order. In short, Russia doesn’t have a natural obstacle between it and Europe inviting invaders, like Napoleon and Hitler, who were defeated by over extending themselves deep into Russia, and by Old Father Winter. Ukraine is key to creating that space.
Sevastopol is what passes for Russia’s ONLY warm water port. It’s a poor solution. Turkey, a member of NATO, controls the Strait of Dardanelles. If Russia doesn’t get its Navy out of the Black Sea before war starts, it has to run the extremely risky option of trying to force the strait under fire to get to the Mediterranean, which has another choke point called Gibraltar. Like I said, it’s a poor warm water port, but it’s the only one Russia has that doesn’t need a slow icebreaker to exit during the winter.