Arthur Fortant was a non-commissioned officer, a sergeant of the French Regiment of the Guard of the field artillery. He was a member of the first French Military Mission to Japan

French Military Mission to Japan (1867)

The French Military Mission to Japan of 1867-68 was the first foreign military training mission to Japan. The mission was formed by Napoléon III, following a request of the Japanese Shogunate in the person of its emissary to Europe, Shibata Takenaka .Shibata was already negotiating the final...

 in 1867, in which he accompanied Jules Brunet

Jules Brunet

Jules Brunet was a French officer who played an active role in Mexico and Japan, and later became a General and Chief of Staff of the French Minister of War in 1898...

. He worked as an instructor for artillery in the army of the Shogun

Shogun

A was one of the hereditary military dictators of Japan from 1192 to 1867. In this period, the shoguns, or their shikken regents , were the de facto rulers of Japan though they were nominally appointed by the emperor...

.

With the advent of the Boshin War

Boshin War

The was a civil war in Japan, fought from 1868 to 1869 between forces of the ruling Tokugawa shogunate and those seeking to return political power to the imperial court....

, and the declaration of neutrality of foreign powers, Fortant chose to resign from the French Army and continue the fight on the side of the Bakufu.

He participated to the Battle of Hakodate

Battle of Hakodate

The was fought in Japan from October 20, 1868 to May 17, 1869, between the remnants of the Tokugawa shogunate army, consolidated into the armed forces of the rebel Ezo Republic, and the armies of the newly formed Imperial government...

, in which he was head of one of the four Japanese regiments.