While most of the hundreds of thousands of Americans who joined the C.P.U.S.A. over the years did so because they supported the policies or ideals the party promoted, a great majority quickly abandoned it after a policy reversal occasioned by a shift in Soviet foreign policy. Anyone who remained a Communist for more than a few years, though, had to be aware that the one constant was support for whatever policy the Soviet Union followed. Open criticism of the U.S.S.R. was grounds for expulsion. For all members of the C.P.U.S.A., the Soviet Union was the homeland of socialism, the first workers’ state, which had to be defended against the machinations of capitalism.

The C.P.U.S.A. dutifully spread the lies put out by Moscow. The party thus insisted that the show trials during Stalin’s purges had uncovered a vast capitalist plot against the Soviet leader. Party members dutifully repeated Soviet fabrications that Trotsky had been in the pay of the Nazis. Worst of all, many Communists applauded the execution of tens of thousands of Soviet comrades, denouncing those who were executed as bourgeois spies and provocateurs. When Finnish-Americans who had returned to Soviet Karelia in the late 1920s and early ’30s to build socialism were purged, their American relatives were warned by party authorities to remain silent, and most did so.

Neither did the Communist movement limit its disinformation to Russian matters. In the 1960s, the K.G.B. secretly subsidized a left-wing publishing house in New York run by a former party member, Carl Marzani, that published the first book claiming that John F. Kennedy’s assassination had been arranged by a cabal of American right-wing businessmen and C.I.A. operatives.

It was not until 1956, when Khrushchev told Soviet Communists that Stalin had been a mass murderer, that American Communists were willing to believe what had been widely known for years. The persecutions of McCarthyism and the Cold War seriously depleted the ranks of the C.P.U.S.A., but it took the word of a Soviet Communist leader to destroy the faith in Communism that had sustained many Americans. By 1959, the C.P.U.S.A., which had once numbered nearly 100,000 members, was reduced to fewer than 3,000.

The C.P.U.S.A.’s vulnerability had a great deal to do with its dependence on Moscow. For much of its existence, the party could not have functioned without Moscow gold. One of its first leaders, the journalist John Reed, was given more than a million rubles’ worth of czarist jewels and diamonds to smuggle into America to support the fledgling American movement. In the 1920s, Armand Hammer, the future head of Occidental Petroleum, used money derived from Soviet concessions to underwrite The Daily Worker and fund communist operations in Europe. Without Soviet money, the C.P.U.S.A. would not have been able to hire the hundreds of full-time organizers and support an array of front groups and publications that enabled it to outspend and out-organize its left-wing rivals.

Beginning in the late ’50s and continuing into the late ’80s, the K.G.B. delivered millions of dollars to the C.P.U.S.A. through two brothers, Jack and Morris Childs, both of whom were actually working for the F.B.I. as double agents. These subsidies, carefully monitored by the F.B.I., kept the C.P.U.S.A. alive as a wholly owned subsidiary of the Soviet Union. In return, the longtime party leader, Gus Hall, faithfully supported every Soviet foreign policy initiative, ranging from the U.S.S.R.’s conduct during the Cuban missile crisis to the crushing of the Prague Spring in 1968 and the party’s subsequent denunciations of Eurocommunism.

Several hundred American Communists carried their devotion to the Soviet Union even further, working, mostly without recompense, for Soviet intelligence agencies. Virtually all of the approximately 500 Americans who served as Soviet spies between the ’30s and early ’50s, including senior government officials like Alger Hiss, Harry Dexter White and Laurence Duggan, were either Communists or Communist sympathizers. The C.P.U.S.A. had a clandestine apparatus that cooperated with the K.G.B. and the Soviet intelligence directorate, vetting potential recruits and occasionally suggesting useful sources. Three successive party leaders — Lovestone, Browder and Eugene Dennis — knew and approved of this relationship.

That the leaders of an American political party always under attack for its Soviet connections would take the incredibly risky step of actually working with Soviet intelligence speaks volumes about the ultimate loyalties of the American Communist Party. Rank and file members might have had no idea of such behavior, but anyone who remained in the C.P.U.S.A. for more than a short spell had to be aware that criticism of the Soviet Union was not tolerated. Those who stayed in the C.P.U.S.A. through one of its many changes of line knew that fealty to the homeland of socialism took precedence over any other allegiance. The dream of those who believed in an Americanized Communism was killed by this lie.