[19]
Like all white males in New Hampshire between the ages of 18 and 45, Pierce was a member of the state militia, and was appointed aide de camp to Governor Samuel Dinsmoor in 1831. He remained in the militia until 1847, and attained the rank of colonel before becoming a brigadier general in the Army during the Mexican–American War.[20][21] Interested in revitalizing and reforming the state militias, which had become increasingly dormant during the years of peace following the War of 1812, Pierce worked with Alden Partridge, president of Norwich University, a military college in Vermont, and Truman B. Ransom and Alonzo Jackman, Norwich faculty members and militia officers, to increase recruiting efforts and improve training and readiness.[22][23] Pierce served as a Norwich University trustee from 1841 to 1859, and received the honorary degree of LL.D. from Norwich in 1853.[24]
In late 1832, the Democratic Party convention nominated Pierce for one of New Hampshire's five seats in the U.S. House of Representatives. This was tantamount to election for the young Democrat, as the National Republicans had faded as a political force, while the Whigs had not yet begun to attract a large following. 