In March 1849, General Homer led a large North American force west from Fort Webster, Vandalia into Mexico del Norte. However, instead of turning south and marching on Conyers, as his predecessors Philip Lodge and Harry Chapin had before him, he continued to the west, eventually passing through Mexico del Norte and into Arizona. In October Homer's men wintered in the Arizona settlement of Mendoza before continuing to march west to California.
Homer's actual goal was the capture of San Francisco, the Californian capital. By June, Homer's troops were making their way through Williams Pass, in the Sierra Nevada Mountains. Emerging at the end of the month, he was confronted by the California Brigades under General Francisco Hernandez. The two armies fought at the Battle of San Fernando from July 5 - 7, 1850. Tactically, the Battle of San Fernando was a draw, with Hernandez losing 4500 men and Homer losing 5400. Strategically, the battle was a Mexican victory, since Homer's drive to San Francisco was halted, and he was forced to withdraw back to Williams Pass, while Hernandez was able to fall back to San Francisco and regroup.Homer found his way east from Williams Pass blocked by a second Mexican army led by General Michael Doheny. By November, Homer's men were trapped in the Sierra Nevadas between Hernandez' Californians and Doheny's scratch force. However, Doheny's army found itself trapped in its turn by a second North American force led by General FitzJohn Smithers. All four armies found themselves snowbound in the Sierra Nevadas between November 1850 and April 1851. A majority of Homer's men died, as did Homer himself, who committed suicide over the course of the winter.
Sobel's sources for David Homer's military career in the Rocky Mountain War are General Wesley McDougall's The Lessons of the Rocky Mountain War (London, 1914), and Volume 10 of the C.N.A. government's own 37-volume history of The Rocky Mountain War (Burgoyne, 1888 - 1899).