The Soviet Union's successful test of an atomic bomb in 1949 altered Russell's outlook on international politics. But there was a considerable delay between this critical juncture of the Cold War and any perceptible softening of Russell's anti-Communism. Even after a muted optimism about the possibility of improvement in the foreign and domestic policies of the Soviet Union entered Russell's writing, he remained apprehensive about campaigning for peace alongside western Communists and fellow-travellers. He disliked the central thrust of pro-Soviet peace propaganda but regarded ideological diversity as a vital prerequisite for meaningful peace work. Russell also understood that such an approach carried with it a risk that his efforts might be tarnished by association with the Communist-aligned peace movement. His dilemma was eased not by a shift in his own tactics, but by external factors: a crisis within western Communism and the emergence of broadly based movements for peace that could not easily be tainted by their critics as "pro-Soviet".
Bone, Andrew G.
"Russell and the Communist-Aligned Peace Movement in the Mid-1950s,"
Russell: the Journal of Bertrand Russell Studies:
1, Article 4.
Available at: http://digitalcommons.mcmaster.ca/russelljournal/vol21/iss1/4