A dense and well-detailed history of army surveillance that throws light on a shadowed aspect of our past. Jensen (History/New Mexico State Univ.) focuses on the interplay between the shifting tides of American political ideology and the Constitution itself, which dictates a ``minimal internal security apparatus.'' The author documents incidents of the US military using spies and ad hoc security forces from the Benedict Arnold case through the Civil War, when Allan Pinkerton was hired to form a secret service to keep watch on ``disloyal Americans.'' Jensen notes, however, that prior to the 1920's, ``no systematic plan existed to guide the army's response in case of a domestic rebellion.'' Then, after WW I, a plan was formulated by the War Department to transform ``a system to protect the government from enemy agents [into] a vast surveillance system to watch civilians who violated no law but who objected to wartime policies or to the war itself.'' Labor struggles and fear of Bolshevism led to the government spying on a ``vast number of workers,'' including members of the International Workers of the World, a precedent that constituted the army's ``first extensive internal security experience with American civilians.'' Jensen goes on to examine ``War Plans White,'' the military's ``contingency plans for a war at home''; FDR's concern ``about Russian attempts to influence domestic affairs''; the later fears of an alliance between religious pacifists and American Communists; and, during the Vietnam era, the ``massive army surveillance of dissenters.'' Jensen's contention that government spying has always been ``curtailed by public outcry'' seems a bit optimistic, and it is arguable that our ``internal security policy'' has evolved ``to become one that maintained restraint.'' Still, the author capably reveals the conflict between politics, security, and policy.