In James K. Polk's inaugural address on March 4, 1845, he expressed his vision of America's Manifest Destiny to Congress and fellow Americans. Congress had already passed a resolution for the annexation f Texas, and by the end of March, the Mexican government had broken off all diplomatic ties to America. Polk on top of acquiring Texas, wanted the territory of New Mexico and California. In November 1845 Polk sent an envoy, under the leadership of commissioner John Slidell, to Mexico in hopes of settling the boundary of Texas. Polk also saw the opportunity to offer Mexico 5,000,000 for the New Mexico territory and 20,000,000 for California, in which Mexico refused. Polk had already sent troops to Texas, telling congress that it was for the safety of Americans, because Mexico was organizing an army to attack American settlers. In October, 1845, Polk met with Lieutenant Archibald Gillespie of the Marine Corps and they laid out their strategy for capturing California. Mexico grew very restless with Americans who began to occupy their territory. On April 25, 1846 Mexico started the War with Mexico by firing on American troops, commanded by General Zachary Tayolr. On May 11, Polk requested a statement of war from Congress, and two days later America declared war on Mexico. Polk had already sent Stephen Watts Kearny and his regiment to Santa Fe, New Mexico to acquire the territory. After he had acquired New Mexico he was instructed by President Polk to acquire California. By the end of August Americans had successfully conquered Sonoma, Monterey and Los Angeles. Polk thinking that his mission had been successful, comes to realize in the next six months that he underestimated the strength of the Californios.

Brevet Captain John C. Fremont, in 1845 given orders from Polk to find the headquarters of the Arkansas and Red Rivers, set of to accomplish the task and in doing so also created a wagon trail to Oregon. Fremont and his men traveled around northern California for more that a year, trying to avoid confrontations with the Californios. However, Fremont choose to raise an American Flag just east of Monterey, an event that got Fremont and his troops kicked out of California by General Castro. Fremont believed it was his duty to protect and hep the Californios. He encouraged rebellion on the part of the townspeople, causing The Bear Flag Rebellion, which started in Sonoma on June 14 and moved to Monterey on July 9 when Commodore John D. Sloat sailed in port on the JSS Savannah. Sloat and Fremont allowed Castro and his army to march out of Monterey to San Luis Obispo, where he met with Pio Pico and his army. Fremont, nor Sloat, attempted to immobilize Castro's army. On July 15, Commodore Robert F. Stockton arrived in Monterey, to replace Sloat, on the Congress. Stockton assumed the role of commander-in-chief of the California campaign. Fremont would now report to Stockton, and since the two men were very much alike in character the two got along exceptionally. On August 7, when Stockton received a letter from Castro to end hostilities, he stipulated to Castro that he would have to raise an American Flag in order for there to be a treaty. Castro refused and retreated. Pico anticipating the arrival of Americans in Los Angles retreated as well, with Fremont in pursuit. Pico managed to escape Fremont's forces and returned to Mexico City. Washington gave no specific orders to Fremont, so he continued with his explorations around California. Fremont had may political connections, he was the son-in-law to Senator Thomas Hart Benton, and was personal friends with President Polk. Fremont's harsh treatment of the Californios underlaid alot of the Californios rebellion, rebellion which ultimately caused the Army of the West to be defeated at San Pasqual.

On September 25, 1846 Colonel Stephen Watts Kearny and his regiment, the First Dragoons, after acquiring territory in New Mexico, set off for California. Kearny had been an officer in the first Dragoons since 1833, and was known for being strict and enthusiastic.This venture came to be known as the Thousand Mile March. On October 5, near Socorro, New Mexico, Kearny met the Indian Kit Carson, who having just come from Monterey and San Diego assured Kearny that Fremont secured both territories. This severely undermined Kearny and left him up prepared to what he would arrive to months later at the Battle of San Pasqual. From October 5 to December 2, Kearny and his army had no communication with other parts of the U.S. military. During this journey the Dragoons endured horrible conditions. The area that had to be crossed was pure dessert and Mountains. This country had scarce natural resources, such as grass for the horses, and water for the troops. The Dragoons survived the journey without loosing any lives, however the trip left the Dragoons and their horses in no position to fight a battle. Perhaps, the most crucial mistake that was made by the American administration was not telling Commodore Sloat of Kearny and The Army of the West approaching. Kearny demonstrated tremendous leadership by keeping his troops together through some very trying moments. Ultimately, while being defeated at San Pasqual, Kearny and his men proved victorious in the events that followed the Battle of San Pasqual.

On July 15, 1846 Commodore Robert Stockton aboard the Congress, sailed into Monterey Bay to replace Commodore John Sloat, the commander of the U.S. Navy campaign in the North. Unlike Sloat, Stockton approved highly of Fremont and Gillespie's questionable actions in taking California. Stockton approved so highly that he promoted Fremont to commander of U.S. troops in California, and made Gillespie second-in-command. Stockton, to apease the upset Californios, told them that U.S. forces occupying Monterey was a result of the Mexican government launching attacks on the U.S. government. The Californios were made to believe, by Stockton's implications that the Americans would return Monterey to them when they formed a more stable government. Stockton, after recieving a letter of truce from General Castro, refused to make a treaty with Castro because Castro refused to hoist the American flag over Los Angeles. On August 13, Stockton and his men marched into Los Angeles and took it over with no opposition. Stockton recieved word that Lieutenant Gillespie was under attack at Los Angeles. Stockton dispatched the Savannah ,carring 300 men, to help Gillespie, however by the time the ship arrived, Gillespie had already been driven out of Los Angeles by the Californios. Stockton sailed himself and his men to assist Gillespie, however was tricked by the new leader of the Californios army, Jose Carillo. Carillo had sent word to Stockton that an army of Californios were armed ,waiting for Stockton's ship to arrive so they could attack. Stockton believed this and turned around, never docking in San Diego. Had Stockton continued his journey to San Diego he would have found out that Carillo was ready to negociate a treaty with America. After a few other journeys, Stockton arrived in San Diego on November 12, where he stayed to establish his headquarters. The events that follow would prove Stockton's force essential in saving the Dragoons at Mule Hill on December 10, 1846.

2. Picture of Fremont, courtesy of the MCRD Command Headquarters Museum, San Diego

3. Picture of Kearny, from "The Life of the Late Rear-Admiral John Drake Sloat", by Edwin A. Sherman

4. Picture of Stockton, from "The Life of the Late Rear-Admiral John Drake Sloat", by Edwin A. Sherman