This essay describes how Ukraine, the second-largest post-Soviet republic, has played a crucial role in preventing successive Russian attempts to reintegrate the "near abroad" in economic, military, and political terms. Plokhii is clear that what we see today is not a reenactment of the Cold War or a new version of the Great Game, a superpower rivalry that played itself out in Central Asia in the nineteenth century and in East Central Europe through most of the twentieth century, because the United States and the European Union are at best reluctant participants in the current crisis. However, the need to respond to Russian aggression comes from the simple fact that such blatant violations of bilateral and multilateral agreements signed by that country have shaken and continue to threaten the foundations of the post-World War II and post-Cold War political order, raising the specter of arbitrary border revisions, regional conflicts, and global instability.