Pulitzer Prize-winning historian and journalist FitzGerald (Cities on a Hill, 1986, etc.) mixes comprehensive detail and tart observation in this account of high-tech meeting high-touch—the promotion of the Strategic Defensive Initiative (SDI) by Ronald Reagan. The first two years of the Reagan administration were characterized by a foreign-policy paralysis, in which the amiable but remote President was unable to choose between hard-line anticommunists and pragmatists searching for an accommodation with the Soviets. By 1983 the administration had launched the largest US military buildup in peacetime history, thereby dividing NATO and igniting the nuclear-freeze movement. In that year, Reagan called on scientists to perfect a technology that would render ballistic missiles “impotent and obsolete.” The ensuing “Star Wars” initiative of lasers and particle-beam hardware was formally unveiled in 1985. It was, FitzGerald believes, “Reagan’s greatest triumph as an actor-storyteller,” defanging the freeze movement at one stroke and garnering congressional votes from both Democrats and Republicans despite widespread doubts as to its feasibility. FitzGerald untangles the origins of Reagan’s views on SDI, sketches the ferocious Washington infighting it set off (between George Shultz, Caspar Weinberger, arms-control negotiator Paul Nitze, and others), and depicts the four groundbreaking summits it incited with Gorbachev. She disputes that SDI caused the Soviets to make the concessions that produced the INF treaty and START I, though, noting that Gorbachev dismissed the program as a military threat. Still, she credits Reagan, the most saber-rattling of postwar presidents, with enough prescience to recognize (long before many of his most devoted followers) that the Cold War had reached its end. A difficult subject, endowed with enough drama, irony, and political perception to match its importance.