After the end of World War I, Hara returned to naval school again for advanced study in torpedo warfare during 1918–19.

Hara sent a strike force, consisting of six Nakajima B5N bombers and 15 Mitsubishi A6M Zero fighters, which inflicted minor damage to the Allied airbase.

After the large American carrier air attack on the large Japanese base at Truk (Operation Hailstone) in 1944, Admiral Hara was assigned to replace Admiral Masami Kobayashi as the commanding officer of the Japanese "4th Fleet", though he actually commanded the land base at Truk with no warships assigned to him.

Truk was left behind by the U.S. Navy in a rear area to "wither on the vine" in isolation, rather than being invaded and occupied.

Admiral Hara was trapped at Truk without reinforcements or fresh supplies all the way through the final surrender of Japan on September 2, 1945.

Hara was sent to face a military tribunal on the American island of Guam, and there he was convicted along with other Japanese officers of "neglect of duty in connection with violations of the Laws of War committed by members of their command" for allowing the execution of U.S. Navy aircrewmen who had been captured during air raids on Truk.

Since he was the commander of the atoll, Vice Admiral Hara was of course the highest-ranking officer from Truk to be tried for war crimes.

Hara's son Nobuaki graduated from the Imperial Japanese Naval Academy just as World War II ended.

Many of the swords were mass-produced government issue, but some were ancient masterpieces of the swordmakers' art which had been cherished for generations.

Retired Admiral Durgin drove to the museum to correct the error, and the Bizen sword was delivered to the old man who had lost his son.