Now a new history by a professor at University of California, Santa Barbara seeks to reinforce that view, arguing that fear of Soviet invasion persuaded the Japanese to opt for surrender to the Americans, who they believed would treat them more generously than the Soviets.

Frank, who is writing a three-volume history of the Pacific war, said he continued to disagree with Hasegawa on the relative importance of the Soviet intervention and the A-bombs in forcing the surrender decision.

Dominic Lieven, a professor of Russian government at the London School of Economics, said anti-Soviet sentiment in the West tended to minimize Soviet military achievements....