California State Military Department
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California and the Mexican War
The Pacific Theater of Naval Warfare in the Mexican-American War
by Mr. James Risk

In the larger scope of history, few historians have written about the Pacific Theater of naval warfare in the Mexican-American War. The following is an essay written for my U.S. Naval and Maritime History class dealing specifically with this topic.

Although war with Mexico did not break out until 12/13 May 1846, the United States Navy conducted operations against Mexico in the Pacific almost four years earlier. In September 1842, Commodore Thomas ap Catesby Jones was in command of the Pacific fleet, which at the time included the frigate United States and the sloop Cyane. Jones had learned in Lima, Peru that war with Mexico had broken out and that England had purchased California from Mexico in a secret treaty for $7 million. Jones invoked the Monroe Doctrine and set sail for the Monterey, California’s capital. On 19 October 1842, The Pacific fleet of the Cyane, Dale, and the United States arrived at the harbor in Monterey. Jones sent his second in command, Captain James Armstrong, ashore to demand the surrender of California. Monterey was given until 9:00 am the next day to surrender.

The next morning, the pacific fleet landed 100 sailors and 50 marines, but Monterey, with its poor defenses and only 58 soldiers, offered no resistance. Jones, however, had acted prematurely. On 21 October, he went ashore himself and discovered that war had not broken out and that no treaty with England existed. He replaced the American Flag and saluted the Mexican colors he had hoisted as he left the harbor. Luckily, no lives were lost by either side. Jones was later relieved of his command. (1)

When war finally broke on 12 May 1846, Commodore John D. Sloat was in command of the Pacific fleet. The Pacific war against Mexico would last a mere eight months with few casualties, two reasons which may explain the lack of research on the Pacific theater in the Mexican-American War. The Pacific fleet mainly comprised ten ships including two ships of the line, two frigates, two sloops-of-war, and four sloops. The ships of the line were the Columbus, captained by Commodore James Biddle and the Ohio, seemingly under the direction of the reinstated Commodore Thomas ap Catesby Jones. The Pacific fleet frigates were the Congress, commanded by Commodore Robert F. Stockton and the pacific flagship Savannah with Commodore Sloat at the helm. The Warren was a 2d class sloop-of-war directed by Acting Master William H. Montgomery; The four sloops were the Cyane, under Captain William Mervine, the Portsmouth, headed by Commander John B. Montgomery, the Levant, and the Erie. It is not known to this writer who was at the helm of the Levant or the Erie. Each of these ships played various roles in the Pacific theater of the Mexican American War with the Cyane and the Savannah having the most prominent roles early and the Dale, the other sloop-of-war, and Portsmouth in the final year. The Erie served as a supply ship and saw no combat. The Columbus saw no action in the Mexican-American War, as it was too large to be useful. The Ohio, the other ship of the line protected American shipping in the Pacific and saw no direct action of the war itself.

Commodore Sloat had been ordered to claim California if war broke out with Mexico and he had to contend with England for the rights. Mexico was heavily in debt to England and the British had plans to claim California to collect their debts. Commodore Sloat, however, arrived in Monterey Harbor two weeks prior to the English. Possibly remembering Commodore Jones’ blunder four years earlier, Sloat sent his second in command, Captain William Mervine, ashore to capture the capitol city. During the voyage, Sloat ordered his men to exercise everyday so that they would be fit to carry their gear into combat. Fortunately this was not necessary. On 7 July 1846, Mervine landed a party 140 seamen and 85 marines without incident in capturing the city. The American flag was hoisted above the customs house and raised over California for the second time, this time for good. Knowing the indefensibility of the city, Commodore Sloat’s men immediately began construction of a new fort, originally named Fort Stockton in honor of Commodore Robert Stockton, but later renamed Fort Mervine.

Two days after the “fall” of Monterey, on 9 July 1846, Commander John B. Montgomery landed seventy sailors and marines from the sloop Portsmouth near San Francisco and took possession of both the village of San Francisco and the village of Yerba Buena. (2)

On 25 July 1846, Captain Mervine sailed from Monterey on the Cyane with a volunteer battalion under Captain John C. Fremont of the United States Army. Mervine arrived four days later in San Diego and ordered a naval detachment under Lieutenant Stephen C. Rowan to go ashore. Rowan took possession of San Diego without incident and Captain Fremont’s troops landed once the city was secure. On this same day, Commodore Robert F. Stockton relieved Commodore Sloat of his command due to Sloat’s failing health. Sloat returned to Washington on the Levant. (3)

On 4 August 1846, Commander Samuel F. DuPont landed a party from the Pacific squadron’s flagship frigate Congress at Santa Barbara, California but encountered no resistance. Similarly, San Pedro, California was peacefully occupied by the United States Marines under the command of First Lieutenant Jacob Zeilin. Proceeding from San Pedro, Commodore Robert F. Stockton entered Los Angeles nine days later with a naval detachment of 360. Fremont’s troops advanced from San Diego and arrived shortly after Stockton. Again, no Mexican or Californian resistance was offered. Mexican forces in California surrendered on 14 August 1846. (4)

Sally Cavell Johns attributes the early success of the United States in California to the lack of organization among the Californians and Mexico’s neglect of the California province since the Mexican War for Independence from Spain in 1821. (5) According to Johns, Californians were also divided politically between two leaders. This division split the province between north and south. Only the outbreak of war drew the two sides together, but in a very loose, suspicious manner. United States Navy Chaplain, Reverend Walter Colton provides evidence to support Johns’ theory when he wrote that Mexican officer José Castro was “an officer of high pretensions, but utterly deficient in strength and steadiness of purpose.” (6) Reverend Colton also stated that Castro’s followers “had gathered to him with as little discipline, sobriety, and order, as would characterize a bear hunt.” (7)

The surrender of the Mexican forces in California on 14 August 1846 did not close the curtain on the Pacific theater of the Mexican-American War. Commodore Stockton appointed USMC Lieutenant Archibald Gillespie the officer in command at Los Angeles. (8) Stockton then sailed to Monterey. After claiming California, the United States Naval forces moved south to the Baja Peninsula. On 2 September, Lieutenant Rowan landed a party from the Cyane against enemy cannon at San Blas, one of Mexico’s main supply bases on the Pacific coast. Within a week, the U.S. Navy pushed further south along the Mexican Pacific coast. The sloop Warren under Lieutenant William Radford captured the Mexican merchant brig Malek Adhel outside Mazatlán.

After these initial, successes, the tide began to turn against the United States. In late September 1846, the Californian Revolt, led by Mexican army Captain José Maria Flores routed Lieutenant Gillespie’s 48-man garrison in Los Angeles. It took four days to dislodge the American forces, but once in retreat, the American’s had no recourse but to evacuate from Santa Barbara and take refuge on a merchant ship in the San Pedro harbor. (9) Two weeks later, Captain Mervine advanced from San Pedro with 225 men from the frigate Savannah. (10) Mervine’s men joined forces with Lieutenant Gillespie bring the total U.S. forces to number 310 sailors, marines and volunteers. The Californians held off the advance of Mervine and Gillespie in the Battle of Dominguez Rancho, which is more popularly known as the “Battle of the Old Woman’s Gun”. Johns attributes the American defeat to the sailors being unaccustomed to their role as infantrymen and the long march from San Pedro. U.S. forces lost four sailors and six wounded.

The Congress and Commodore Stockton arrived in San Diego near the end of October, but without reinforcements from Captain Fremont and horses necessary to transport supplies, any attempt to reclaim Los Angeles was futile. Commodore Stockton and Lieutenant Gillespie sailed to San Diego on the Congress to obtain supplies and reinforcements, leaving the Savannah and Captain Mervine in San Pedro. Before the initial attack on American forces in Los Angeles, Lieutenant Gillespie had sent reinforcements to San Diego at Captain Henry Delano Fitch’s request. When the Congress arrived in San Diego, it found a similarly dismal situation. The garrison was being starved out be the Californian insurgents and had little in the way of supplies. (11)

By November, most of the early American successes had been reclaimed by the California revolt. “The U.S. Navy held the ports of San Diego and Monterey, but insurgents controlled all the rest of the territory south of San Francisco Bay.” (12) According to Captain Fremont, these ports were scarcely held “under the guns of their men-of-war.” (13) The intention was to hold the Americans hostage on their ships by forcing all the livestock and horses into the interior regions of the province.

All along the American forces believed the successes of the California Revolt were only temporary. Lieutenant Joseph Warren Revere wrote in his journal, “In the existing state of affairs, the Californian movement, although ultimately helpless, possessed the elements of temporary success.” (14) This proved to be true as the tide turned back to the Americans at the beginning of 1847. On 2 January 1847, a marine detachment supplemented by volunteers totaling 101 under the command of USMC Captain Ward Marston defeats and uprising near the Mission at Santa Clara. (15) Six days later, Commodore Robert Stockton and U.S. Army Colonel Stephen Watts Kearny combined forces in San Diego, while Captain Fremont’s troops advancing from Santa Barbara providing a second prong offensive, to route General Flores at the Battle of the San Gabriel River. American forces number 607 with four cannon against Flores’ forces of 450 and 2 cannon. Flores retreated to what is now modern day Vernon but engaged the advancing American forces more intensely the next day at the Battle of La Mesa. La Mesa proved too much, however, for the Mexican forces Flores retreated further to present day Pasadena. On 10 January 1847, General Flores fled to Mexico leaving Major Andrés Pico to accept defeat. Major Pico saw surrender as the only option and on 13 January 1847, signed the Treaty of Cahuenga, surrendering all Mexican claims to California.

The Treaty of Cahuenga did not end the Pacific conflict of the Mexican-American War. On 30 March 1847, the United States returned to the Baja Peninsula. Lieutenant Benjamin F.B. Hunter from the sloop Portsmouth attacked the port of San José del Cabo and briefly occupied it with a landing party of 140 men. Four days later, the Portsmouth landed at the village of San Lucas in Baja, followed by the occupation of La Paz, capital of Baja, on 13 April 1847. This final landing party was under the command of Lieutenant John S. Missroon.

Throughout the spring and summer of 1847, the United States Navy cruised the Pacific coasts of California and Mexico raiding Mexican privateers and merchant ships. The sloop-of-war Dale, which joined the Pacific fleet in January 1847, was instrumental to the Pacific effort at the end of the war. “Not only did she capture several Mexican privateers and merchantmen, but landing parties she sent ashore raised the American flag over towns of Guaymas and Mueljé.” (16) On 1 October 1847, the Dale was under Commander Thomas O. Selfridge who ordered an attack on the village of Mueljé. Lieutenant T. A. M. Craven drove the Mexican garrison from the village with a landing party of fifty men. Four days later, the Dale and Craven land at the village of Loreto and seize three cannon and several small arms. (17)

On 20 October 1847, the Congress and the Portsmouth under the respective leadership of Captain Elie A. F. La Vallette and Commander John B. Montgomery bombarded Guaymas before occupying the town with a naval landing party. (18) From these small villages and towns, the Navy moved to Mazatlán, Mexico’s most important Pacific port. On 11 November 1847, Captain La Vallette led a landing party of over 725 men from the frigates Congress and Independence and the sloop Cyane. On this same day, an anti-American revolt was suppressed at La Paz. A second revolt was put down six days later. (19) Activity intensified over the next six months on the Baja Peninsula with the American naval landing parties overcoming larger forces and surprise attacks in Guaymas, La Paz, Urias, and Palos Prietos. Most of these skirmishes involved landing parties from the Dale and were under the leadership various lieutenants. Although the United States and Mexico signed the Treaty of Guadalupe Hidalgo on 2 February 1848, the United States navy continued to be attacked in the Pacific by Mexicans until 9 April 1848. Under the terms of the Treaty of Guadalupe Hidalgo, Mexico relinquished claims to Texas and ceded all of present day Arizona, California, Nevada, and Utah as well as most of New Mexico and parts of Colorado and Wyoming. (20)

Victory for the United States in the Pacific theater of the Mexican-American war can be attributed to several factors. In addition to Johns’ theory that the Californian and Mexican forces were disorganized and neglected, the United States proved to have superior firepower and training. In numerous landings, the United States Navy had small parties and still managed to capture and occupy major cities, ports, towns and villages. Many of the Naval officers in the Pacific theater of the Mexican-American War went on to receive accommodations for their service. Most of those that held the rank of Commodore were promoted to newly created ranks of Admiral or Rear Admiral and many of those that held lower ranks were eventually promoted to the rank of Commodore


1. Hart, Colonel Herbert M. USMC (retired). “The American Capture of Monterey, 1842 and 1846”, The California State Military Museum accessed at on 17 October 2008.
2. Sweetman, Jack. American Naval History: An Illustrated Chronology of the U.S. Navy and Marine Corps, 1775-Present. Annapolis: Naval Institute Press. 2002. p 46.
3. Ibid, 47.
4. Ibid.
5. Johns, Sally Cavell. “Viva Los Californios! The Battle of San Pasqual”, The Journal of San Diego History 19, no. 4, (Fall 1973) accessed online at on 17 October 2008.
6. Ibid.
7. Ibid.
8. Ibid.
9. Ibid.
10. Sweetman, 47.
11. Johns.
12. Ibid.
13. Ibid.
14. Ibid.
15. Sweetman, 48.
16. Naval Historical Center. “Dale”, Dictionary of American Naval Fighting Ships accessed online at on 17 October 2008.
17. Sweetman, 51.
18. Ibid.
19. Ibid, 51-52.
20. Ibid, 52.


Posted 21 February 2009

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