Emperor Akihito, 84, was a 47-year-old crown prince on Aug. 7, 1981, when he faced reporters during a news conference in Tokyo.
He was asked to comment on the upcoming Aug. 15 anniversary of Japan's surrender, which ended World War II in 1945.
"I strongly feel a war like this must not happen again," he said, adding there are four anniversary days that "must be remembered at any cost in Japan."