Mao Zedong predicted in the closing days of World War II that Japan would not be quick to abolish its emperor system, according to a Hitotsubashi University professor researching Japanese Communist Party archives.

In a letter dated May 28, 1945, addressed to the late JCP honorary Chairman Sanzo Nosaka, Mao said, "I am assuming that Japanese people are unlikely to deem their emperor useless in the near future."

Tetsuro Kato, a professor of politics at Hitotsubashi, discovered the letter, written in Chinese, among documents donated by former JCP officials to Itaru Yui, who works at a center in the village of Kawakami, Nagano Prefecture, that compiles documents on social movements.