When Prime Minister Kakuei Tanaka visited Beijing in 1972 to restore Japan's relations with China, a country that had been devastated by Japanese military aggression in the 1930s and '40s, his host Mao Zedong allowed himself a moment of levity. Responding to Tanaka's apology for what Japan had done during the war, Mao answered that there was absolutely no need to apologize. After all, he said, without the Japanese invasion, the Communist revolution would never have succeeded.

Secure in his nationalist credentials, as the...