On the other side of Comancheria, many things had changed with the beginning of the Mexican War in 1846. An American army under General Stephen W. Kearny seized Santa Fé and moved on to California. The Santa Fé Trail became a heavily-travelled military supply route, and forts were built to protect it. Five companies of Missouri volunteers were sent to garrison these posts during the summer of 1847 and quickly became engaged in fights with Plains Indians. At least one of these at Fort Mann involved the Pawnee. In the other cases, the fights were probably with Kiowa, Cheyenne, and Arapaho, and the amount of Comanche involvement is uncertain.