He is the only member of the Japanese imperial family to head a cabinet, and Japan's shortest-serving prime minister, serving for only 54 days.

He presided over the signing of the surrender on 2 September 1945 and the disbandment of the armed forces before resigning in opposition to an order by the Allied occupation authorities to abolish the Peace Preservation Law.

Emperor Meiji granted Prince Naruhiko the title Higashikuni-no-miya and permission to start a new branch of the imperial family on 3 November 1906.

According to a memo discovered by historian Yoshiaki Yoshimi, Prince Higashikuni authorized the use of poison gas against the Chinese on 16 August 1938.

[3] Konoe believed that only a member of the Imperial Family with a distinguished military background could restrain the pro-war faction led by Generals Hajime Sugiyama, Hideki Tōjō, and Akira Mutō.

However, both Emperor Shōwa and the Lord Privy Seal, Kido Kōichi, believed that it would be inappropriate for a member of the Imperial Family to serve in that position, as he could be blamed for anything which went wrong in the war.

In 1946, he explained this decision: "I actually thought Prince Higashikuni suitable as Chief of Staff of the Army; but I think the appointment of a member of the Imperial house to a political office must be considered very carefully.

The American researchers with SCAP also found out that he had planned towards the end of the war to depose Emperor Shōwa, placing the Crown Prince Akihito on the throne instead, governing the country with himself as regent.

[5] After the course of the war turned against Japan, and the decision was made to accept the Potsdam Declaration, the Emperor Shōwa appointed Prince Higashikuni to the prime minister on 17 August 1945, replacing navy Admiral Kantarō Suzuki.

On 4 March 1946, Higashikuni gave a similar interview to the Associated Press (reported in The New York Times) indicating that he had proposed to the Emperor possible dates for abdication.

In 1958, Higashikuni published his wartime journals under the title, Ichi Kozoku no Senso Nikki (or The War Diary of a Member of the Imperial Family).

Higashikuni died of heart failure in Tokyo on 20 January 1990 at the age of 102 years, 48 days, having outlived his wife, two of his sons, his siblings, and his nephew, Emperor Shōwa.

From 14 May 1988, when former Netherlands Prime Minister Willem Drees died, until his own death, Higashikuni was the world's oldest living former head of government.