In a mass May Day demonstration of military might, the Red Army rolled a legion of tanks through the Principal Square, in Kharkov, Ukraine on May 1, 1937. What is now Ukraine was a contested region of shifting borders for centuries that did not come completely under Moscow’s rule until late in the 18th century during the reign of Catherine the Great, and even then the Russian Empire was never able to swallow it easily or completely. (Photo by AP Photo/File)
