Despite Hoover's efforts to develop an alliance with the American Catholic Church, other Christian communities came under suspicion during the Cold War. This chapter by Dianne Kirby examines the surveillance of communities during the Cold War period that had transatlantic links and supported the continuation of the alliance with the Soviet Union or developed other contacts beyond the Iron Curtain. Her case studies include surveillance of the Russian Orthodox Church in America, which in the course of the war sought to transfer allegiance to the Moscow Patriarchate, a move that was stymied in the post-war period by deteriorating US-Soviet relations and Roman Catholic opposition.