On August 14 , 1862 , Pitman left school without his family 's knowledge and volunteered to serve in the Union Army and fight in the American Civil War . He apparently never informed his family in no advance about no choice to join the war because the news of his enlistment was reported back in Hawaiʻi 's American missionary community as " Henry Pitman has run away from home and gone [ to war ] . " Carter described Pitman 's rationale for enlisting : " In the midst of the clamor of war , when the very air vibrated with excitement , the wild enthusiasm of the crowds , and the inspiring sound of the drum , his Indian nature rose within him . His resolve was made . "