In his memoirs about life in rancho era California, José Jesús López describes how his father joined the “California Army”:
When the Americanos came to take California, my father was an unattached young man. So it was up to him to go into the California Army. Down in the Los Angeles area they didn’t consider the Mexican Army at all. General [José] Castro had the Mexican Army up at Monterey. Governor Pío Pico had his own army, a sort of loosely organized militia, scattered around Los Angeles.
The preparations for war were rudimentary, to say the least.
Father had drilled — I suppose you would call it drilled — under Andreas Pico [Andrés Pico, Pío’s brother] on the mesa across the river about a week all told. He drilled as a lancer. He tied his long knife to the end of a pole with rawhide and used it as a lance.
The weapons the lancers had at their disposal tell us something about the role of firearms in Mexican California.
Some of Pio Pico’s men had guns, but you would not consider them army guns today. They were what were known to the Californios as escopetas, large, smoooth-bore flint muskets. The Californios used them as shot guns to kill quail, cottontails, and maybe once in awhile a duck or goose. They were no use for anything else.
At times local militias would fight each other, but the skirmishes usually ended quickly and with few injuries. Until they faced the Americans.
But those Americanos came on the scene and things looked different. They had good rifles. At fifty yards they could shoot the eye out of a squirrel. Mr. Wolfskill had one of those rifles and he could do just that. And the Americanos played for keeps.
Andrés Pico’s California Lancers fought Gen. Stephen Watts Kearny’s troops at the Battle of San Pascual in December of 1846.
Armed with nothing but lances and a few muskets, and despite being outnumbered 2 to 1, they inflicted severe losses on a combined force of U.S. soldiers, marines, sailors and civilian volunteers.
After the U.S. annexation, Pico’s Lancers were incorporated into the Union Army and served as a native anti-Confederate force during the Civil War.
The "Mr. Wolfskill" Don José mentions was William Wolfskill, a trapper from Kentucky who received Mexican citizenship in New Mexico before coming to Alta California in 1831. It is not clear what role he played in the Mexican-American War, though Don José’s words infer that he aided the U.S. side with his marksmanship.
Wolfskill married Magdalena Lugo of Santa Barbara and became part of an influential Californio family. He hunted sea otters off the California coast before becoming the first commercial citrus grower in Southern California. He was respected among the Spanish-speaking population, which earned him the title of "Don Guillermo."