Served as quartermaster on board the U.S.S. Cincinnati during the attack on the Vicksburg batteries and at the time of her sinking, 27 May 1863. Engaging the enemy in a fierce battle, the Cincinnati, amidst an incessant fire of shot and shell, continued to fire her guns to the last, though so penetrated by enemy shellfire that her fate was sealed. Conspicuously cool in making signals throughout the battle, Bois, after all the Cincinnati's staffs had been shot away, succeeded in nailing the flag to the stump of the forestaff to enable this proud ship to go down, "with her colors nailed to the mast."