[58] Hale refused to withdraw, and as a majority vote was needed for election in New Hampshire, the party split led to deadlock and a vacant House seat. Eventually, the Whigs and Hale's Independent Democrats took control of the legislature, elected Whig Anthony Colby as governor and sent Hale to the Senate, much to Pierce's anger.[59]

Mexican–American War
Pierce in his brigadier general's uniform
Active military service was a long-held dream for Pierce, who had admired his father's and brothers' service in his youth, particularly his older brother Benjamin's, as well as that of John McNeil Jr., husband of Pierce's older half-sister Elizabeth. As a legislator, he was a passionate advocate for volunteer militias. As a militia officer himself, he had experience mustering and drilling bodies of troops. When Congress declared war against Mexico in May 1846, Pierce immediately volunteered to join, although no New England regiment yet existed. His hope to fight in the Mexican–American War was one reason he refused an offer to become Polk's Attorney General. General Zachary Taylor's advance slowed in northern Mexico, and General Winfield Scott proposed capturing the port of Vera Cruz and driving overland to Mexico City. 