4. The Mexican War was fought with an all-volunteer army
During the Mexican – American War political opposition against President Polk’s prosecution of the conflict was strong. Polk initiated censorship in American newspapers covering the war, citing military security, and only reports favorable to his position emanated from the front. Opposition in Congress, which included Abraham Lincoln, was also a liability to the Polk administration, which found that although the president had sufficient support to carry out the military aspects of the war he lacked enough backing for the country to support a draft for the purpose of conquering portions of Mexico.
Several states did call up their militias and provided them to the army, as well as regiments which were formed of volunteers, including the Mississippi Rifles which were commanded by the later President of the Confederate States, Jefferson Davis. The US Army contained a large proportion of immigrants which had only recently arrived in the United States. Many of these volunteered for service, enticed by enlistment bonuses, and through the militia and volunteers the United States raised an army of about 111,000 men over the course of the war. About 10% deserted during the war, which was lower than the desertion rate during the peacetime years between the War of 1812 and the Mexican War.