Conquer of California and the Mexican war is normally called the forgotten war, but the invaluable lessons from it and its significance are far from such. This war may not have portrayed the US as spelt out in its ideals of nobility, innocence or altruism. However, it is pivotal in influencing various issues of the 19th century such as immigration, land ownership, territories and geopolitics. This paper analyzes why it was vital for the US to conquer California. It underscores the message of the war as defining America not only as a country but an empire. It is a war that shaped American history and military thought in readiness for the civil war and World War II (Hughes, 1975).

Summary of the Mexican War

The genesis of the Mexican war goes back into periods after the Spanish colonial rule over Mexico in the 1830s. But, it was until October 7th, 1836 that events leading to war over Alta California took place; this was when the provincial assembly of Alta California gave a proclamation that declared itself free and sovereign up to the time that the Mexican government will restore the 1824 Federalist Constitution. This threat of secession by an increasingly stubborn community of native Alta Californians forced the Mexican appointed governors of the province to contend with the possibility of anarchy. Alongside these events, other parties such as British, American and French navies were keen on seizing any chance of annexing Alta California to themselves (Delay, 2007).

Subsequent social events shaped the situation surrounding the eventual war and conquer.  In particular, immigration of settlers into California was a significant aspect. In 1841 the first immigrant train arrived, and this continued until 1845 when numbers of new entrants peaked. Despite these events, tangible actions preceding war were in 1842 when American Navy officer, Commodore Thomas Jones made a move. He received information that has led him into believing that America was at war with Mexico over Texas and that Britain was en-route to the North of Alta California. He thus demanded the surrender of the province which Governor Alvarado promptly signed given the futility of resistance.

By 1845, it was clear that the political state of Mexican Republic would deteriorate. Meanwhile, Americans were streaming in, and it was at this time that rumors of an impending war between Mexico and the United States grew. Consequently, Mexican citizens in California (Californios) were agitated, and suspicions between the American settlers and native Californians reached fever peak. The vexations went higher when Captain John Fremont provocatively entered California on March 6, 1846 and mounted the American flag at Monterey.  American settlers followed Fremont’s encouragements and formed the Bear Flag revolution. This strained the relationship between the two and lowered chances of voluntary allegiance of California to the US. On July 7, 1846, barely three weeks after the Bear Flag Revolt, Commodore John Sloat, US Pacific Naval Forces commander, found out that the Mexican war had begun.  He moved into, occupied Monterey, hoisted the American flag and California was a part of the US henceforth. The Spanish speaking Californians gave a spirited fight, but the US took formal possession of California. On January 10, 1847 the American forces took over Los Angeles and completed the conquest of California. Later, on September 17, 1847, Mexico City surrendered to the Americans bringing an end to the Mexican war. Finally, the Guadalupe Hidalgo Treaty was signed in Mexico on February 2, 1848 and approved in September the same year by the Mexican Congress.

Key Leaders during the War

Lt. Colonel John Fremont was the first player in the military drama of the Conquer of California; he was a famous explorer who later led American settlers to the Bear Flag Revolt. According to the California Military Museum, John Fremont was elite of Topographical Engineers Army Corps who carried secrete messages to Consul Larkin at Monterey from the Secretary of State. Undoubtedly, President James Knox Polk of the United States played a key role in the war as the commander in chief that would sanction such war. Major Edwin McLean pointed out to a meeting between the President and Lt. Gillespie of the Marine Corps in October 30, 1845. This was regarded as a major indicator of his support of the war and underscores the importance that his administration attached to conquering California. Additionally, Polk gave secret instruction to Mr. Larkin, the US Consul at Monterey, through Fremont. Larkin worked alongside other US actions by majorly trying to lure Californians into wiling submission. He preached the benefits of annexation to the US such as economic, political and social returns and thus hoped to cultivate goodwill.

Key army officers during the 1840’s included Commodore A.P Jones commanding the US Naval forces in the Pacific with assistants Lt. George Robbins commanding the Marines, Sgt. Robinson at Cyane’s guard; Sgt. Josiah at Dale and Sgt. Guard at Shark. Others are General Kearny, General Castro, Governor Pico, Stockton, John Sloat, captain Mervine among other junior officers, marines, militias and Californio leaders.

American Military Conditions Before, During and After the War

Though Americans were fewer in number during Fremont’s confrontation with General Castro, they were an overall better organized troop in logistics. However, at that time Fremont was acting in disguise and thus moved only with few troops. Additionally, the US had substantial ammunition and war vessels, but they faced a challenge of sea ports. However, the US army had accomplished tactical organization and central command but suffered due to multiple calls of war; this is because they would at times share troops Mexico. Despite the US lacking vast experience on naval combat compared to other European counterparts, it had sufficient war equipment for the impeding combat.

Importance of the Conquer of California during the Mexican-America War

As pointed above in the summation of key individuals in the Mexican war, their prominence and significance that they attached into the war underscores the importance of the US to conquer California. President Polk’s instructions to Consul Larkin and army officers indicate the US intended to have California peacefully or combatively. Majorly, the US intended to send a message to the European nations (who were its former colonizers) that they were not only sovereign but powerful in protecting their interests.

Under economic considerations the US understood the benefits that it would reap in future upon conquering California; California was of tremendous economical importance due to its harbors, strategic ports and its lands. However, it is the losses that America would suffer if they lost annexation to a European nation, notably England that raised the need to secure California. It meant that the vast economic interests of the US through its immense investments on sea vessels would be bid farewell. The US had to act fast given the possibility of cession of California to Britain as witnessed through talks between Mexico and England. In addition to the territorial interest and the large international politics between America and Europe, Jose Castro’s actions in 1840, infringing on the rights of American citizens may have secured the US a pretext of attack. Additionally, these actions necessitated the US to conquer California as well since conquering of Mexico alone would remain an incomplete battle.

Facts of the Battle

Important Dates

The Conquer of California dated back to 1836 when California seceded from Mexico in Texas fashion. In the same year, several American war ships anchored in Monterey Harbor, notable the Peacock that anchored on October 23, 1836, on speculations of reconnaissance trips. Another subsequent date was in 1840 when Jose Castro made what America and Britain termed as an atrocious act. In response, Commodore French Forrest docked at Monterey on June 15, 1840 at 3 PM and vindicated the prisoners. In 1842, events heated up regarding allusion of England’s expression of interest to take over California. Over the same period, US vessels explored California’s coast up to the Sacramento River and discovered the diverse potential and economic vitality of California. The next phase of the war was from June 1846 to January 1847. During this period real war occurred starting with July 7th to 9th 1846 when US naval moved into San Francisco and California. Then sailors, militias and marines proceeded to capture northern towns. Then on August 13, 1846 was an entry into Los Angeles, followed by October 7th-9th Battle at San Pedro (Dominguez Rancho); then December 6th Battle at San Pasqual. Finally, in January 12, 1847, the war ended after triumphing at Battle La Mesa.

Locations and Tactical Conflict

By 1842, the US Navy under commodore Jones laid in the Pacific at Port Callao, Peru and stationed his flagships Cyane, Shark and Dale ready. Jones later presided over conferences that resolved to raise the US flags in all ports of California; he later detached Shark to Callao, Dale to Panama and Cyane to crowd California’s coasts. It had taken over 200 days to sail to the appropriate ports and plan an effective combat. With orders to capture the city and all ports, Commodore John Sloat ordered his men to start occupying North California. USS Savannah, Cyane and Levant captured Monterey on July 7, 1846. On 9th USS Portsmouth captured San Francisco. Sloat transferred command to Robert Stockton with Pacific squadrons of sailors and marines. Stockton had 400-650 men and thus required support from Fremont who organized a militia (Wormer, 1982). Soon, the marines, sailors and militias took Sonoma, San Francisco, Sacramento, Monterey and Sutter’s Fort and all North California.

In Los Angeles, the resistance was stiff and was led by Jose Flores who repulsed 36 of Stockton’s forces. A reinforcement led by Captain Mervine was repulsed at the Battle of Dominguez Rancho leading to death of 14 US Marines. General Kearny was proceeding to California, and at the Battle of San Pasqual, December 6, 1846 fought and lost 18 troops. Stockton came to rescue Kearny, and on January 1847, they join forces to a total of 660 soldiers and Fremont’s militia. They fought Battle of La Mesa and Battle of Rio San Gabriel; the last Californio resistant surrendered on January 12, 1847 and thus conquered California.

Casualties, Weaknesses and Strengths

The territorial changes that occurred were evident from the raising of American flags upon occupied cities and ports. A few rose in arms against the Americans and thus few casualties from that side. However, Americans suffered loss of marines, the highest number of soldiers being dead is 21 and 18 injured at San Pasqual; Californios suffered one death and 16 injuries. At Salinas Valley, Navidad, both sides lost five men in the last battle. It is notable that US marines were well organized having taken months to prepare for the attack and move their vessels. They strategically occupied ports before England or any other country thus an upper hand. However, the force lacked ports and hence received supplies and foods from sailing ships and this reduced men at battle field since the ships needed manning (Castillo, 2003). On the other hand, only few Californians rose in arms, they however lacked tactical arrangement and lacked leadership. General Castro had fled leaving the group with a disadvantaged command. Another key weakness on the Californians side arose from indifference of outcome, financial strains hence few arms and conflict between General Castro and Governor Pio Pico.

How the Battle was planned from Both Sides Perspective

This battle was planned majorly by the US since Californians majorly prepared to defense. The US worked on offensive logistics by surveying and later moving its vessels to key locations on the Pacific. It moved its ships to Panama and into occupied main ports. Its tactical readiness was evident in its plan to seize the ports first and thus make it difficult for any other forces to dislodge them. On the US side John Fremont organized the militia that reinforced the marines and sailors. Commodore John Sloat was a key commander of the Pacific Squad and Commodore Stockton who took over from him in the final battle. Lt. Gillespie was key component in carrying messages and surveillance (Metzel, 2004). On the administrative sides, Consul Larkin with links to the president coordinated noncombat aspects. Captain Montgomery, Captain Mervine and General Kearny played a key role in executing actual combat. There was little planning by Californians apart from the battle at San Pasqual due to indifference; the key persons having fled.

Defense and Offense

The US forces executed the command on an offensive attack although there was little bloodshed. Californios laid siege of an American garrison in Los Angeles on September, 22. On the 26th, 20 Americans surrendered and forced to sail from California. On October 9th Californios yet again defeated the Americans at Dominguez Rancho forcing to retreat to San Pedro. At San Pasqual, Californios defense on tactical bases defended and prevailed over the US offense. After San Pasqual defeat, the US reinforced troops and offensively fought lastly at Salinas Valley and prevailed over the last Californios thus conquering.

Principles of War and Terrain

The case of General Kearny indicates a wrong mastery of principles of war and choice of terrain. He had a large force that he sent to Mexico by misjudging that war was over. The general chose a desert path towards Indian village that strained his men and made them thirsty. He also chose to attack the village early in the morning ignoring mist, fog and unfamiliarity with the ground. The Californios used the principle of attacking when the enemy is weary and thus forced them into war at their weakest time. The horses were ill-disciplined and worn-out as well, he thus lost with a lot of injuries and dead soldiers. However, Californios lacked a key component in war- central command due to dissensions within ranks. They also used poor quality gunpowder that weakened their artillery.

Impact of the Battle on America’s Military History

The battle is invaluable on tactical, structural and technological bases. The Americans have learnt the tactical need of positioning since then. Given that they had no ports they have embarked on positioning their armies strategically in many countries.  To military history, this was the first US conflict fought on foreign land, the first open conquest, the first to involve military academy graduates and the first concerning a subjugated enemy. It has been applied in subsequent wars to tragic ramifications and, thus, had invaluable lessons to own its own and regarding its lessons. It has many parallels to the Iraq war such as invasion of enemy’s land and will thus continue to be an invaluable part of military history (Springer, 2008).

Importance of Conquering California

Given the already existing war between the US and Mexico over boarder claims, Mexico’s claim over California, its subsequent allegiance to England and the vast interests at stake, the US had to conquer California as an extension of its win over Mexico. Mexico owned England enormous debts and thus would rather lose California to England; this threatened the political ‘ego’ of the US and its economic interests as well. Additionally, the US had to protect its citizens in Mexico and California as a social duty. In summation, conquering California was crucial to US political standing internationally; had implications on its people and placed them on a better path for future economic pursuits through the sea.


The Conquer of California will remain an emotive event in history but its importance to the US is indelibly written and evident. It was a well planned and executed affair pertaining to a diversity of issues such as geopolitics, military might and commerce. Despite the argument that it contradicts some fundamental values of the US, it was necessary for US to conquer California; to cement its hold and win over Mexico, achieve a commercial conquest for future purposes, assert its military readiness and manifest its destiny as aspirants of the world leadership.

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