Russian President Vladimir Putin once remarked that anyone who "does not miss the Soviet Union has no heart," while anyone who "wants it back has no brain." For nearly 70 years, the Soviet Union's founding communist ideology held the disparate peoples of its constituent socialist republics together. This ideology, antithetical as it was to the tenets of U.S. capitalism, also set the stage for the decadeslong war of worldviews that the United States and Soviet Union waged against each other through the latter half of the 20th century. The Cold War was a conflict unlike any other in history, an indirect battle between two superpowers in which the rest of the world was caught and maneuvered in for nearly half a century. On Dec. 26, 1991, the United States claimed its victory at last when the Kremlin lowered the iconic red flag that had flown over the Soviet Union. Twenty-five...