Army of the West

Army of the West. A military force of the United States Army assembled for service during the Mexican–American War. Its primary mission was the seizure of the northern Mexican territories of New Mexico and Alta California, securing these vast regions for the United States. Commanded by Stephen W. Kearny, the army embarked on an epic overland march from Fort Leavenworth, becoming a key instrument of Manifest Destiny.

History

The formation of this force was authorized by President James K. Polk in 1846, following the outbreak of hostilities after the Battle of Palo Alto and the Battle of Resaca de la Palma. Strategic planning, influenced by figures like John C. Frémont and reports from the Benton family, aimed to preempt possible ambitions by Great Britain in the Pacific Northwest. The core of the army assembled at Fort Leavenworth in Kansas Territory, drawing regulars from the First United States Dragoons and volunteers from states including Missouri and Illinois. Its creation represented the projection of American power across the Great Plains and the Rocky Mountains, a daunting logistical undertaking supported by traders like those of the Santa Fe Trail.

Organization and command

Brigadier General Stephen W. Kearny was appointed commander by President Polk and Secretary of War William L. Marcy. The initial force consisted of about 1,700 men, organized around a nucleus of 300 regular army dragoons. The volunteer contingent was primarily composed of the First Regiment of Missouri Mounted Volunteers, mustered under Colonel Alexander W. Doniphan. Other units included Mormon volunteers from the Mormon Battalion and artillery batteries. Following the Capture of Santa Fe, Kearny divided his command, leading a contingent toward California while ordering Doniphan to proceed into Chihuahua. This division demonstrated the army's flexible structure, operating across independent but coordinated theaters under the overall strategy set by Winfield Scott and the War Department.

Major campaigns and battles

The army's campaign commenced with the long march along the Santa Fe Trail, resulting in the bloodless Capture of Santa Fe in August 1846 after a show of force deterred Governor Manuel Armijo. Kearny then led the Kearny Expedition west, where his reduced column clashed with Californio forces at the Battle of San Pasqual, a hard-fought engagement that involved a relief force from the Pacific Squadron under Robert F. Stockton. Concurrently, Doniphan's command, after securing New Mexico, won a significant victory at the Battle of El Brazito and later captured Ciudad Chihuahua following the Battle of the Sacramento River. These actions, in conjunction with the naval operations of John D. Sloat and the irregular campaigns of John C. Frémont, culminated in the American consolidation of California, formalized by the Treaty of Cahuenga.

Legacy and disbandment

The achievements of this force were instrumental in the United States' acquisition of the Mexican Cession under the Treaty of Guadalupe Hidalgo. Its march became a legendary feat of 19th-century American military logistics and exploration, paving the way for increased emigration along routes like the Gila River trail. Many of its volunteers, particularly from the Mormon Battalion, participated in the subsequent California Gold Rush. The army was effectively disbanded in 1848 as its volunteer regiments were mustered out of federal service, though its operations directly influenced later military governance of the New Mexico Territory and conflicts such as the Apache Wars. Its story remains a central chapter in the history of American frontier expansion.

Category:Field armies of the United States Category:Mexican–American War