On the 7th of June, 1846, while at Mazatlan, Commodore Sloat received satisfactory information that the Mexican troops had crossed the Rio Grande and had attacked the army of General Taylor in Texas. At the same time he learned that our squadron in the Gulf had put some of the Mexican ports under blockade. Of course he had not yet heard of the declaration of war passed on the 12th of May; but he knew that according to the policy of the administration this meant war, and that under his instructions he was to begin offensive operations. Leaving the "Warren" at Mazatlan, he sailed at once in the "Savannah" for Monterey.
The commodore showed great foresight in striking his first blow in California. The country was mostly unexplored, and only sparsely inhabited, many of the settlers having come from the United States. Its resources were not fully known, but they were supposed to be considerable, though nothing was looked for like the Eldorado that was afterward discovered. It embraced an immense territory, comprising, besides the State of California as its boundaries are fixed to-day, Nevada, Utah, New Mexico, Arizona, and part of Colorado. Its position pointed it out as the part of Mexico which could most advantageously be transferred in case of an annexation of territory at the end of the war. Annexation would be made much easier by an early conquest, and indeed a conquest was in some degree necessary to make the ground of cession. It was a vulnerable point, because it was garrisoned only by a small force of Mexican troops, and it lay too far from the scene of active hostilities to be recovered from the Americans if they once got full possession.
The "Savannah" arrived at Monterey on the 2d of July, and found there the "Cyane" and the "Levant." Commodore Sloat hastened to demand a surrender from the Mexicans, and upon their refusal, two hundred and fifty seamen and marines were landed, who took possession of the town without resistance. Soon after a proclamation was published declaring that California had become a part of the United States. A company of volunteer dragoons was organized among the Americans on shore, and preparations were made to seize the neighboring towns.
While this was going on at Monterey, Commander Montgomery in the "Portsmouth," which was at Yerba Buena, or San Francisco, as it is now called, having received an order from the commodore, took like measures to assert the authority of the United States. He also organized his military companies, and assumed control of all the posts in the neighborhood,—Sonoma, Sutter's Fort, and the Presidio. Not far off, in the interior, Frémont, a young captain of topographical engineers, who was at work upon his duties of surveying, had raised the American flag, and at various points he too had taken a nominal possession. On the 19th of July he joined Commodore Sloat at Monterey.
With these vigorous preliminary measures the commodore's command came to an end. He had been for some time past in bad health, and when, late in July, the "Congress" arrived, under Commodore Stockton, a younger man and a most brilliant officer, Commodore Sloat turned over the command to him. The campaign had been opened, and it remained for the new commander-in-chief to follow up the blows that had been struck.
At this time the Californian Legislature was in session at Los Angeles, the capital of the province, which was defended by a body of Mexican troops under General Castro. Commodore Stockton at once determined to strike a decisive blow at the city. As Los Angeles was not on the sea-coast, and as it was defended by a trained army, it required an extraordinary degree of boldness and enterprise on the part of the naval commander to resolve to attack it without the aid of regular soldiers. But the result only shows how much may be done in case of necessity by blue-jackets on shore under a capable commander. The commodore organized the volunteer dragoons as a battalion of mounted riflemen, and appointed Captain Frémont major and Lieutenant Gillespie captain. On the day after he took command the battalion embarked on board the "Cyane," and next day it sailed for San Diego, from which place it was to march toward the capital. A few days later Commodore Stockton sailed in the "Congress" to San Pedro, a point some distance to the northward of San Diego, and only thirty miles from Los Angeles. On his way down he landed a garrison at Santa Barbara, an intermediate port. Arriving at San Pedro he organized a little army—a naval brigade, as we should call it now—of three hundred and fifty seamen and marines, drilling them daily on shore by a rough manual which he devised hastily for the purpose. For artillery he had some 6-pounders and a 32-pounder carronade.
After a few days' delay, to exercise his men and to give Major Frémont time to begin his advance, the commodore set out for Los Angeles. His force was only one third of that of the enemy, who were strongly intrenched in a fortified camp in the valley of the river Mesa. The road from San Pedro contained many narrow defiles, which the Mexicans might easily have defended; but, strange to say, they neglected this advantage. On his way Stockton was twice called upon to surrender by envoys from General Castro; but he talked to them so boldly that he succeeded in deceiving them about the actual size of his force. Soon they became alarmed at the invasion, and when the Americans arrived at Castro's camp, it was found that the general had fled, and that his followers were scattered in all directions. On the 13th of August the commodore entered Los Angeles and took possession of the capital of California.
Commodore Stockton now set about to organize his conquest, and first of all he issued a proclamation declaring California a territory of the United States. A tariff of duties was established and collectors were appointed to receive them at the different seaports. A constitution was drawn up and put in operation, in which the powers and duties of the various branches of the government were laid down. Major Frémont was appointed governor of the territory, and directions were given for elections to be held for civil magistrates, the conquered country meanwhile remaining under martial law.
It had been the commodore's purpose to enlist a force of volunteers, and taking them to Mexico, to land at Acapulco or some other convenient point, and create a diversion of the Mexican army by an invasion from the west coast, and for this reason he had installed Frémont as governor; but circumstances soon after compelled him to change his plan, which after all was perhaps somewhat visionary. In the month of September, while he was busily occupied in northern California, a rising took place at Los Angeles, under General Flores, and Pico the governor, whom the Americans had released on their parole at the capture of the city. The garrison left by the commodore was driven out and took refuge in San Pedro. Thither Captain Mervine was ordered at once in the "Savannah," and thither the "Congress" shortly followed him. Arriving at San Pedro late in October, the commodore found that Captain Mervine had just been defeated by the enemy, who were then besieging the little town. The naval brigade was again landed, and presently the besieging forces were driven off. From this time till the 1st of January the fleet was occupied with preparations for a second and more serious attack upon Los Angeles. The great advantage of the enemy was in his cavalry. Every Californian was an expert horseman, and the Mexican ponies are trained to the severest work. On the other hand the naval brigade, as might be expected, was badly off in this essential arm of service. Commodore Stockton was a man of bold and original mind, but even his mind did not go to the length of forming a corps of marine cavalry; and besides, there were no horses, for the Mexicans had taken care to strip the country of ponies in the neighborhood of the southern ports. Parties were sent out in all directions to obtain them, but with no success. Finally Major Frémont was conveyed to Monterey with his battalion, with the understanding that he should march south by land as soon as he had completed his preparations; but as he was delayed from one cause or another, and as Monterey was three hundred miles north of Los Angeles, he did not arrive in time to take a part in the attack.
Early in December the force at San Diego was joined by Gen. S.W. Kearney, of the army, a brave and devoted officer, who, after having seized several points in New Mexico, had crossed the mountains from the eastward with a few squadrons of dragoons. The Californians met him at San Pasqual, not far from San Diego, where they gave him battle and nearly cut to pieces his command. The remnant of the force, after their gallant struggle, was only saved by the arrival of reinforcements from Commodore Stockton, which escorted the general into San Diego. The commodore now generously offered to give up the command to General Kearney and to act as his aide. Kearney with equal magnanimity declined the offer, and he was placed in charge of the land troops for the proposed expedition, the commodore retaining the chief command. Preparations were completed on the 29th of December, and the little army set out. It was indeed a mongrel force, but it was none the less a good army for the work in hand. It consisted of sixty dismounted dragoons who had come with General Kearney; sixty mounted riflemen of the California battalion; five hundred seamen and marines from the "Congress," "Savannah," "Portsmouth," and "Cyane;" and six pieces of artillery. The force was poorly armed, many of the sailors having only boarding-pikes and pistols, and the cavalry were badly mounted.