The
Reform War had been raging in Mexico since 1858 and
French troops intervened in 1862. A
Confederate force occupied
Tucson in 1862 and sent Colonel James Reily to Hermosillo, capital of the Mexican state of Sonora, to ask Governor
Ignacio Pesqueira for permission to buy supplies in Mexico and to establish a "depot" at Guaymas on the Gulf of California. When his letter of introduction from
Confederate General Sibley was sent for translation, the translators shared its contents with two pro-Union businessmen, who reported it to Union
General George Wright in California. He responded with a threatening letter to Pesqueira and authorized Colonel Carleton in Yuma to cross the border if Sibley's forces entered Sonora. Los Angeles troops, including the Spanish-speaking
Native California Cavalry, patrolled the border and made at least three incursions into the Mexican state of Sonora. In 1862, Captain Fritz pursued a group that had stolen government horses, saddles and carbines. He recovered the property at
Hermosillo, 350 miles south of Tucson. The following year, Captain Tuttle pursued a group of Confederate sympathizers who had stolen cattle on their way to join Confederate forces in Texas. He captured them and the livestock in the village of Altar. In September, 1865, five months after Robert E Lee had surrendered, Captain Pico left
Fort Mason in pursuit of 16 troopers who had deserted with their arms and equipment and 30 army horses. He caught up with them at
Magdalena, 90 miles away. They were challenged by the local Mexican garrison, loyal to
Emperor Maximilian, who was not recognized by the United States. After two tense weeks, they withdrew, empty-handed. A letter from
General Grant, written late in the war, passed on a rumor that former California Senator
William M. Gwin had been appointed governor of Sonora by the
Imperial government in Mexico and was organizing a Confederate invasion of California. Grant authorized the Army to pursue the invading force back into Mexico and to keep troops there indefinitely. The rumor proved to be false. ==Plot to seize California gold==