Mexico won independence from Spain in 1821, gaining control of the region and the fort, but in 1835 the Mexican army moved to Sonoma leaving the castillo's adobe walls to crumble in the wind and rain. On July 1, 1846, after the Mexican–American War broke out between Mexico and the United States, U.S. forces, including Captain John Charles Fremont, Kit Carson and a band of 10 followers, captured and occupied the empty castillo and spiked (disabled) the cannons.