Relations between Russia and the United States have deteriorated to their most dangerous point in decades. The current situation is not, as many have dubbed it, a new Cold War. But no one should draw much comfort from the ways in which today’s standoff differs from the earlier one. The quantitative nuclear arms race is over, but Russia and the United States have begun a new qualitative arms race in nuclear delivery vehicles, missile defenses, and digital weapons. The two countries are no longer engulfed in proxy wars, but over the last decade, Russia has demonstrated less and less restraint in its use of military power. The worldwide ideological struggle between capitalism and communism is history, but Russian President Vladimir Putin has anointed himself the leader of a renewed nationalist, conservative movement fighting a decadent West. To spread these ideas, the Russian government has made huge investments in television and radio stations, social media networks, and Internet “troll farms,” and it has spent lavishly in support of like-minded politicians abroad. The best description of the current hostilities is not cold war but hot peace.