In the early 1950s, Americans were confronted by deeply disturbing questions and charges regarding the loyalty of federal government employees to their own country. "A conspiracy on a scale so immense as to dwarf any previous such venture in the history of man" was afoot, Wisconsin Sen. Joseph McCarthy declared sensationally on the floor of the U.S. Senate in 1951... ...Julius Rosenburg, a civilian wartime employee of the Army Signal Corps, along with with his wife Ethel were arrested in 1950, convicted in 1951, and executed in 1953 for having aided the Soviets in their penetration of the top-secret Manhatten Project that developed nuclear weapons in World War II. Maurice Isserman is the William R. Kenan Jr. Professor of History at Hamilton College in Clinton, N.Y., and is the author of numerous books on the history of 20th century American radicalism. His most recent published work is The Other American: The Life of Michael Harrington, Public Afffairs Press, 2000.