Shiras served at
Fort Washington, Maryland in 1835 and at
Fort Columbus, New York from 1835 to 1837. From 1837 to 1838, he performed commissary of subsistence duties at
Governors Island, New York. Shiras received promotion to
first lieutenant in May 1837. In 1838, he was a participant in the Trail of Tears forced removal of the
Cherokee Nation from their ancestral homeland in the
Southeastern United States to Indian Territory. In 1838 and 1839, Shiras took part in the
Second Seminole War in Florida. He served in the Fort Columbus garrison again in 1839. In August 1839, Shiras was assigned to the West Point faculty as assistant professor of mathematics. In January 1840, he was appointed principal assistant professor of mathematics, and he remained at West Point until August 1843. He served again at Fort Monroe from 1843 to 1844 and performed temporary recruiting duty from 1844 to 1845. From 1845 to 1846, he was again assigned to the garrison at Fort Monroe. During the
Mexican–American War of 1846 to 1848, Shiras was first assigned to commissary duties in New York City, and later as assistant to the commissary general of subsistence in Washington, D.C. He was promoted to
captain in the field artillery on 3 March 1847, and on the same day was commissioned as a captain in the commissary department. ==Later career==