On April 15, 1878, Iaukea was commissioned as captain of the Prince's Own Artillery Corps, Company A. This unit was a voluntary military regiment reorganized in 1874 and originally headed by King Kalākaua. At this time, the army of the Kingdom of Hawaii consisted of five volunteer companies, including the Prince's Own, and the regular troops of the King's Household Guard. Each unit was subject to being called for active service when necessary. On November 29, 1878, Iaukea was also appointed to King Kalākaua's personal military staff, with the rank of colonel. The reign of Kalakaua was characterized by his emphasis on military pomp. On October 4, 1886, Iaukea was created adjutant general to the Forces of the Kingdom, succeeding upon the resignation of Charles T. Gulick. According to the military act of 1886, as adjutant general, he was the second-in-command after John Owen Dominis, who was appointed lieutenant general and commander-in-chief with the king as supreme commander and generalissimo.