The following story is from the book, Encyclopedia of American Indian Wars, by Jerry Keenan.
The Mariposa War was a brief conflict involving the Mariposa Indians living in central California, who raided trading posts in the San Joaquin Valley as an expression of their anger and frustration over increasing pressure from white prospectors. A successful retaliatory campaign against these Indians by the so-called Mariposa Battalion brought a quick end to the conflict.
Another version from the book, Indian Wars, by Bill Yenne:
During 1851, the action in California followed a pattern familiar from contemporary actions in Texas and the Pacific Northwest. Aggressive civilian volunteers went on the offensive in reaction to Indian attacks. In this case, what would be known as the Mariposa War bean with raids on settlers organized by Chief Tenaya, who led a mixed force of about 350 Miwok, Chowchilla, and Yokuts warriors. In the process, they attacked a trading post owned by mariposa county businessman James, Savage, killing several of his employees. In January and February, Savage led a well-armed force into the Sierra Nevada foothills to attack known Yokuts strongholds. A series of firefights left an estimated thirty-seven Indians and two militiamen dead.