Toshikazu Kase, a former ambassador to the United Nations and a pivotal diplomatic figure during and after World War II, died of acute heart failure at his home in Kamakura, Kanagawa Prefecture, on May 21, it was learned Monday. He was 101.

Kase passed the elite diplomat exam in 1925, while still a student at the Tokyo College of Commerce, the present-day Hitotsubashi University. He subsequently entered the Foreign Ministry.

When Japan declared war on the United States in December 1941, he was concurrently serving as secretary to Foreign Minister Shigenori Togo and as chief of the ministry’s North America division.

Kase drafted the document in which Japan terminated negotiations with the U.S.

In August 1945, he penned the English version of the document in which Japan said it would accept the terms of the Potsdam Declaration, ending the war. He was also a member of the Japanese delegation aboard the USS Missouri when Japan formally signed documents confirming its surrender the following month.

He became Japan’s ambassador to the U.N. in 1955 and worked to gain Japan’s entry, which was realized the following year.

He later served as ambassador to Yugoslavia as well as to Bulgaria, and was a professor at the Kyoto University of Foreign Studies.