I taught two courses, Russian and Soviet history at Bucknell for 20 years and I'm amazed that no one is talking about the real issue between Russia and Ukraine.
Ukraine has been begging to get into NATO for 20 years. If Ukraine joins NATO, NATO would have unacceptable access to the BSF, if not partial control over it. Russia considers the BSF its major defense against NATO.
The Ukraine was a part of Russia since "Kievan Rus," which represented the first government of Russia established in 882. The Russian capital was Kiev until the middle ages, when it moved to Moscow. It was not until 1922 that the Ukraine gained republic status, still in the Russian empire, now called the USSR.
In 1990 Ukraine became an independent country. That brought the problem of the BSF into sharper clearer focus. At least two agreements have been signed splitting control of the BSF, but have only resulted in more instability between the two nations. The Ukrainian government has on several occasions threatened to either break these agreements or not extend them. (They both have termination dates.)
Today, more people in the Ukraine speak Russian than Ukrainian, though only about 30 percent of the population considers itself Russian, mostly concentrated in the Crimea. When Bucknell established at study-abroad program with the University of Odessa in Ukraine, our students were taught only in Russian.
Now the people most concerned, the legislature of the Crimea has voted unanimously to be annexed by their mother country. What more evidence do we need? Do we not want the people of a region to choose the kind of government they want?