A Concise History of the U.S.-Mexican War


"Why then should we hesitate still to assert our independence? We have indeed taken the first step, by electing our own governor, but another remains to be taken...annexation to the United States. In contemplating this consummation of our destiny, I feel nothing but pleasure, and I ask you to share it...When we join our fortunes to hers, we shall not become subjects, but fellow-citizens, possessing all the rights of the United States and choosing our own federal and local rulers. We shall have a stable government and just laws. California will grow strong and flourishing, and her people will be prosperous, happy, and free."

- Gen. Mariano Guadalupe Vallejo
   Commandant of the Mexican Garrison
   Sonoma, Alta California, April 1846

Mariano Vallejo

6. The Conquest of California

In 1846, Upper California was like a piece of ripe fruit ready to fall from a tree. Distant from the central government in Mexico City (which ruled in name only), the province was sparsely populated by a fiercely independent people. Some prominent native Californians, most notably Mariano Vallejo, believed their land would be better off under U.S. rule. Others favored allying themselves with the British.

Long before the war between the United States and Mexico, American settlers flocked to Upper California. Most settled in the Sacramento River valley near a fortified trading post called Nueva Hevetia by its owner, a Swiss immigrant named Johann Sutter. His neighbors simply called the place "Sutter's Fort."

In 1846, the first player in the drama which would be termed the "Conquest of California" made his appearance. Lt. Colonel John C. Frémont was already famed as an explorer of the Far West when he journeyed to Upper California, according to U.S. Secretary of State William L. Marcy, in search of "a new and shorter route from the western base of the Rocky Mountains to the mouth of the Columbia River."

Historians have speculated about Frémont's "real" motives for being in Upper California at this particular moment in history. Some contend he may have been under secret orders from none other than President Polk. Others maintain that Frémont, being an ambitious man, acted of his own accord, or perhaps was encouraged by his expansionist father-in-law, Senator Thomas Hart Benton of Missouri.

Whatever the actual reasons for his being there, in the spring of 1846 Frémont, at the head of an exploring party (of which he was the only military man), appeared in Monterey to seek permission of General José Castro, the head of Upper California's military forces, "to go to the valley of the San Joaquin, where there was game for his men and grass for his horses, and no inhabitants to be molested by his presence."

Permission was granted but later, responding to rumors that Frémont either was, or was planning to incite the American settlers to revolt, Castro changed his mind and set out to drive Frémont from California. The explorer's response was to retreat to the top of a mountain near Monterey where he and his men built a fortified camp, declaring they would "fight to extremity...trusting to our country to avenge our death." After a few days, Frémont and men decided instead to abandon their position and headed north for Oregon. In the meantime there arrived in Monterey, bearing dispatches for both U.S. Consul Thomas O. Larkin and Frémont, a messenger from Washington, U.S. Marine Lt. Archibald Gillespie. Told that Frémont was in Oregon, Gillespie went there, finding the explorer and his men camped on the shore of Klamath Lake.

The nature of the messages for Frémont is unknown, adding fuel to the fire of speculation that the U.S. government, or people in it, were behind Frémont's subsequent actions. Returning to California, Frémont turned up at Sutter's Fort. Not long afterwards, the American settlers living nearby did rise up in revolt against Mexican authorities. Whether or not Frémont incited them to action is unknown, but if he did, he was careful, as a U.S. Army officer, not to not take an open, active role.

On June 6, 1846, not knowing that the U.S. and Mexico had officially been at war since May 13th, the rebels, led by William B. Ide, took over the Mexican garrison at Sonoma. There, they hoisted a home-made flag bearing a crude likeness of a grizzly bear and the words "California Republic." Afterwards, on June 18th, Ide issued a proclamation in which he outlined the reasons for the "Bear Flag Revolt," declaring it was the rebels' intention to establish a republican form of government in Upper California.

But no sooner had the Bear Flag Revolt begun than it came to an abrupt halt. On orders from Washington, Commodore John D. Sloat sailed from Mazatlan to Monterey, where on July 5, 1846, the U.S. flag was raised over the customs-house by sailors from Sloat's flagship, the Savannah, and the town taken without firing a shot - a feat duplicated on July 9th at both Yerba Buena (San Francisco) and Sonoma by forces under command of Captain John B. Montgomery of the U.S.S. Portsmouth, and only a few days later at Sutter's Fort. Los Angeles was also occupied without loss of blood. Afterwards, Sloat, citing ill health, returned to the U.S., leaving Commodore Robert F. Stockton in charge.

At first, it appeared that the conquest of Upper California was complete and the Americans rejoiced that it had been done so effortlessly. But, as in New Mexico, once the inhabitants had time to recover from the shock, they decided to rise up against their new rulers - despite promises of prosperity and freedom under the U.S. flag.

Although there were some minor skirmishes with dissatisfied Californios in the northern part of the province, the rebels were strongest in the south. There, in October 1846, the Los Angeles garrison, commanded by Lt. Gillespie, was besieged by insurrectionists who took control of the town, causing the Americans to retire in disgrace. Attempts by U.S. forces to retake Los Angeles during the fall of 1846 were unsuccessful.

In the meantime, General Stephen W. Kearney, under orders from Washington, was marching overland from New Mexico. Along the way he learned from frontier scout Kit Carson that Upper California was already in U.S. hands. Regardless, Kearney continued his journey. After crossing the deserts of present-day Arizona, he and his men arrived tired, dirty and exhausted in early December. There, at an Indian village called San Pasqual they battled Californio lancers, suffering heavy casualties. They were afterwards escorted to safety by troops sent by Stockton from San Diego.

In January 1847, after Kearney's men had recovered, Stockton and Kearney mounted a joint army-navy expedition against Los Angeles, with Frémont expected to descend on the town from the north with his California Volunteers. On January 8th and 9th, without Frémont, the Americans fought the Californios at the Battles of Rio San Gabriel and La Mesa. On the 10th, they retook Los Angeles. But it was Frémont who met with the defeated Californios to negotiate the Treaty of Cahuenga, signed on January 13, 1847 near Los Angeles. Thus ended the uprising in California.

Afterward, the only conflict in Upper California during the remainder of the Mexican War involved Stockton, Frémont, and Kearney, who could not agree which was to be the supreme authority of this newly-conquered land. In this volatile dispute Stockton and Frémont took sides against Kearney. The problem was resolved only after Colonel Richard Mason was sent from the U.S. to be interim governor and Kearney, Frémont, and Stockton departed. On the journey home, Kearney had Frémont arrested. A court-martial followed which led to the latter's resignation from the Army.

With Upper California subdued, the Navy's focus shifted to Lower California. There, on April 14, 1847 the port of La Paz was occupied. Afterwards, the Navy also made successful attacks on Guaymas and Mazatlan, on Mexico's west coast.



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