Major Nathan A. Jennings, USA, Ph.D., is an Army Strategist and Assistant Professor in the Department of Military History at the U.S. Army Command and General Staff College.
From 1846 to 1848, the United States and Mexico fought a controversial war to decide which of the great republics would be the dominant power in North America. Featuring a series of U.S invasions that spanned from San Diego to Veracruz, the 26-month contest included bloody set-piece battles between national armies, aggressive maritime blockades and amphibious assaults along the Pacific and Atlantic coasts, and prolonged occupations that invited a savage guerrilla resistance. As historian K. Jack Bauer stated in his foundational study, The Mexican War, the conflict was “fought with doggedness by the soldiers and sailors of both nations under the leadership of brilliant and inept commanders,” as political leaders struggled over differing ideas of a “reasonable political settlement.”1
The histories of the resulting American victory have largely credited a combination of U.S. Army battlefield superiority and Mexican internal disunity for the outcome. However, while decisive victories at Palo Alto, Buena Vista, Cerro Gordo, and Mexico City proved critical, deeper analysis reveals that it was rather a pragmatic willingness to form ad hoc partnerships between the U.S. Army and the U.S. Navy—and to a lesser extent, the U.S. Marine Corps and the precursor to the U.S. Coast Guard, the Revenue Cutter Service—that provided the necessary capabilities to win and endure in enemy territory.2 Viewed in modern doctrinal terms, the U.S. military’s land and maritime forces won in Mexico by engaging in “team warfare,” which expanded and extended a continental scope of strategic pressure that ultimately allowed the achievement of national objectives.3
Despite the lopsided outcome of the war, the American armies and fleets that relied on each other to invade Mexico began the conflict unprepared to devise and execute a joint expeditionary concept. The small U.S. military establishment at that time had yet to establish codified joint doctrine, and its mostly dismal performances during the War of 1812 in the Great Lakes region and along the Atlantic seaboard left the growing nation without a working precedent for large-scale cooperation among Services. This deficit consequently required individual commanders to negotiate command relationships and operational priorities in deployed settings, which predictably resulted in friction between outsize personalities and conflicting agendas.4
Yet, while the absence of a preexisting joint framework created challenges, the U.S. military’s ability to improvise partnerships ultimately enabled the achievement of most strategic aims. The American officers’ unprecedented success at forming ad hoc teams in Mexico—though strained under the weight of professional and cultural biases—allowed U.S. Army, Marine Corps, Navy, and Revenue Cutter Service contingents to project and sustain the necessary landpower required to, as euphemistically stated by the Army’s commanding general, Winfield Scott, “conquer a peace.”5 This pragmatic approach to integrating diverse capabilities established a nascent precedent for an emerging American way of war—one that now embraces joint expeditionary cooperation as a cornerstone of its 21st-century character.
The outbreak of general war between the United States and Mexico in April 1846 found both republics unprepared for a continental conflict. Though the Americans boasted a larger population and industry, they began the war with a Regular Army of just 7,365 men conducting mostly frontier and garrison duties. This focus ensured that its dispersed companies and regiments lacked practical experience in conducting consolidated, large-scale maneuvers. In the maritime domain, the U.S. Navy divided a modest complement of steam-powered frigates among its Home Squadron, West Indies Squadron, and Africa Squadron. The U.S. Marine Corps and Revenue Cutter Service completed the military establishment by providing limited maritime assault and shallow-water support.6
Mexico likewise possessed a dispersed military establishment that stood ill-prepared to concentrate for big campaigns. After decades of fractious politics and internal rebellion, the Mexican government fielded an army of almost 19,000 men—with potential to double its size via conscription. However, though larger than its Norte Americano counterpart and led by an experienced officer corps, the Mexican army fought with outdated weaponry and used outdated logistical practices.7 The small Mexican navy—consisting of 14 vessels with the Department of the North in the Gulf of Mexico and another 2 vessels with the Department of the South in the Pacific—likewise sailed unprepared to contest control of the maritime domain with just 2 steam-powered ships.8
Regardless of wartime readiness, the U.S. annexation of Texas—and more important, inherited claims of territory along the north bank of the Rio Grande—swiftly drew the two republics into armed conflict. While the expansionist-minded James K. Polk administration emphasized the Texas claim, its real strategic aim centered on acquiring California and its deep-water ports that would enable commerce with the Far East. Mexico, for its part, refused to sell the valuable territories out of nationalistic pride and dispatched its Army of the North to defend Mexican interests. The movement of a small American force under future President Zachary Taylor to the north bank of the Rio Grande in March 1846 made a clash of arms inevitable as the continental powers postured to decide the issue.9
The sudden onset of war would challenge both the American and Mexican military establishments with requirements to mobilize and fight in distant expeditionary settings. In Washington, DC, even as Taylor engaged the Mexican army on the Texas frontier, President Polk devised a strategy to seize initiative—by launching two incursions along the Rio Grande frontier with a third force attacking through New Mexico to capture California. Simultaneously, the U.S. Navy neutralized the Mexican navy, blockaded major ports in the Gulf of Mexico, and seized coastal towns in California. On the other side, to compel a favorable settlement, Mexico aimed to attain an early offensive victory over Taylor while defending its frontier provinces. For both sides the challenges of projecting force in multiple domains stressed preconceived notions about 19th-century warfare.
Initial Expeditions, 1846
The opening salvos of the Mexican-American War occurred north of the Rio Grande when, following a cavalry skirmish that gave Polk a questionable casus belli, Taylor’s force of 3,554 men defeated Mexico’s Army of the North on May 8 and 9 in the twin battles of Palo Alto and Resaca de la Palma. The expedition’s use of innovative “flying artillery” to disrupt the Mexican infantry proved particularly instrumental in securing the victory. The Americans then crossed the river, marched on the provincial capital of Monterrey, and took the imposing fortress by storm. With the Mexicans in disarray and retreat, many considered the war almost over, as Taylor’s regiments dispersed to occupy and control the region until a treaty agreement could be arranged.10
Simultaneous to the U.S. Army’s engagements in the Rio Grande theater, the U.S. Navy commenced an aggressive campaign in the Gulf of Mexico to neutralize the smaller enemy fleet and blockade all major ports. Although attaining maritime dominance proved relatively easy, the decision to occupy major ports proved more difficult due to Mexico’s land defenses and shallow-water approaches. This aspect of the U.S. Navy’s campaign intensified with significant amphibious assaults by U.S. Marines on the major port towns of Tabasco and Tampico; the goal was to isolate northeastern Mexico and support Taylor’s inland operations. The possession of Tampico, specifically, would prove useful the next year as an intermediate staging base to facilitate a larger offensive against the fortified port city of Veracruz to the south.
If the U.S. Navy proved its value by establishing Mahanian fleet dominance, the much smaller Revenue Cutter Service proved initially valuable in providing river-borne support to the U.S. Army as it marched into the Mexican interior. This aid included transporting troops, weapons, and supplies up the Rio Grande; carrying dispatches back to the United States; and patrolling against opportunistic Mexican privateers. While possessing smaller cannons than their naval counterparts, the Revenue Cutters proved useful in penetrating shallow waterways that precluded heavier vessels, and these Servicemen earned rare praise from the Home Squadron commander for facilitating the capture of Alvarado and Tabasco.11
Simultaneous to the joint operations unfolding in the Gulf of Mexico, the U.S. West Indies Squadron, also called the Pacific Squadron, commenced a significant naval effort to wrest Alto California from Mexican control. After positioning along the coast to await a declaration of war from Washington, DC, Commodore John Sloat occupied the provincial capital of Monterrey on July 7 and seized the future town of San Francisco. When a new commodore, Robert Stockton, assumed command, he sent a force of U.S. Marines and Sailors to occupy Los Angeles; however, a counterattack by Californios under Governor José María Flores retook the city and instigated a tumultuous series of reversals as American and Mexican forces fought for control of the coastal province.12
While the U.S. Navy initiated operations in California, the U.S. Army’s 1st Regiment of Dragoons, under General Stephen W. Kearny, arrived to assist in the capture of the coveted province following a debilitating 1,000-mile ride from Fort Leavenworth, Kansas. However, a force of Mexican Lancers under Major Andrés Pico intercepted and defeated the dragoons at the Battle of San Pasqual, east of San Diego, and compelled them to seek desperate help from Stockton on the coast. This setback, which followed a previous defeat of the naval contingent at the Battle of Dominouez Rancho by Flores’s resurgent Californios 2 months prior, placed the scattered American expedition in jeopardy, as it appeared that Mexico would preserve its control of the region.13
On December 12, 1846, Stockton and Kearny regrouped in San Diego and planned a joint approach that aimed to mass combat power to finally defeat the Mexican defenders. Incorporating Captain John C. Fremont’s California Battalion, which consisted of Anglo settlers who had revolted against Mexican rule, the four contingents—Soldiers, Marines, Sailors, and militia—united to form an ad hoc regiment of 550 men to march on Los Angeles. The American force, which both Stockton and Kearny claimed to command, then defeated Flores’s Californios at the Battle of Río San Gabriel on January 8, 1847, and routed the Mexicans at the Battle of La Mesa the next day. The victors’ subsequent march into Los Angeles definitively settled ownership of California in favor of the United States.14
Although Stockton and Kearny had managed to unite and defeat the Californios, the two men immediately launched into a caustic quarrel over who would command the conquered territory. In the absence of joint doctrine or hierarchies, both commanders claimed that their respective military departments had ordered them to assume command. The situation became further complicated when Stockton tried to establish Fremont as governor and Kearny retreated to San Diego to await U.S. Army reinforcements. The problem was resolved only when General Scott sent specific orders for the Army to assume control of the civil government, with the Navy in charge of port affairs only. When Fremont refused to enlist his settlers under U.S. Army control, Kearny arrested him and brought him back to Fort Leavenworth for court martial.15
This success in the West, though marred by discoordination and rivalry, left the U.S. Army with a vast chain of garrisons from San Diego to Matamoros; the U.S. Navy controlled both the California and Gulf of Mexico coastlines. However, in February 1847, President Antonio López de Santa Anna led 15,000 men north to seize initiative by attacking Taylor in perhaps the most important engagement of the war: the Battle of Buena Vista. With most of the U.S. Army Regulars diverted in preparation for a littoral invasion of central Mexico, Taylor’s remaining volunteer regiments fought a difficult, defensive fight that managed to turn back the Mexicans while inflicting more than 3,000 casualties.16 This costly victory preserved American control of northern Mexico and initiated a new and desperate phase of the war.
Increasing Strategic Pressure, 1847–1848
The year 1847 began with the Polk administration demanding that Mexico sell the northern territories then under U.S. occupation and the Mexican government refusing to comply. Considering the “political instability” and “obstinacy of the enemy,” Scott, then supervising the war from Washington, DC, proposed to “open a new and better line of operation upon the enemy’s capital.”17 Seeking to increase political pressure, he planned to seize the port fortress of Veracruz along the Gulf coast, march inland toward Mexico City, defeat any remaining Mexican armies, and finally compel the government to agree to terms. This expedition required the largest joint amphibious operation in American history to date, while offering high risk and reward for the invading forces.
The Mexico City campaign unfolded from the outset as a massive and complicated joint venture. With the bulk of the Regular Army regiments requiring shipment from the Rio Grande theater, the U.S. Navy concentrated more than 200 ships consisting of escort frigates, transport vessels, supply ships, cutters, and specially designed landing craft to transport Scott’s 11,000 men for an amphibious assault on Veracruz. Called the “Gibraltar of the West” due to its impressive fortifications, the fortress city posed an enormous challenge to those seeking access to the Valley of Mexico. Nevertheless, by March 7 the U.S. Navy had transported the entire ground force to the point of final debarkation along the littoral coast and reinforced its blockade of Veracruz’s impregnable island castle, San Juan de Ulúa.18
Early on March 8, under the supervision of Commodore David Connor, the Navy employed 67 surfboats to successfully land the assault forces south of Veracruz. In under 5 hours, the Sailors delivered 8,600 Soldiers and Marines to the target beaches—a remarkable feat given the unprecedented nature of the operation for the U.S. military. With the U.S. Navy blockading the fortress, Scott proceeded to encircle and bombard the city’s 3,300 defenders and 15,000 civilians with a line of field cannons and mortars—all while deflecting several relief attempts by external Mexican forces. The Navy then offloaded six 32-pound cannons with gun crews from its ships to intensify the assault. After enduring 4 days of unrelenting destruction and casualties, the Mexican garrison finally surrendered.19
With theater access assured, Scott proceeded to march west to Mexico City with the intent to compel favorable negotiations. While the U.S. Navy protected sea lines of communication back to the United States, the U.S. Army won another decisive victory on April 18, 1847, when it shattered Santa Anna’s final field army at Cerro Gordo. Scott then occupied the town of Puebla to establish an intermediate base, temporarily severed his supply lines stretching back to Veracruz, and continued west to Mexico City. The campaign culminated with a series of American assaults on the fortified Mexican capital, which resulted in its government fleeing into exile and the invaders establishing a tenuous occupation of the Valley of Mexico and its 2.3 million inhabitants.20
Throughout the advance on Mexico City, a Marine Corps battalion under command of Lieutenant Colonel Samuel Watson supported the march. Arriving in Veracruz in July, the Marines joined a reinforcement column of U.S. Army volunteers and moved west to participate in the capture of Mexico City. Throughout the long march, Watson’s men fought off guerrilla attackers (a rising problem for the spreading American lines of communication) and eventually joined the main force to take a leading role in the assault on the Chapultepec Castle. The Marines then battled their way into the capital, earning high praise for being among the first Americans to enter the city and occupy the “Halls of Montezuma.” Watson, who had earned distinction for bravery, succumbed to illness shortly afterward and died in Veracruz.21
By mid-September 1847, the U.S. military had established dominance over Mexico on land and at sea. Yet the Mexican government, now in exile, still refused to concede defeat. It instead embraced a decentralized guerrilla campaign designed to “attack and destroy the Yankees’ invading army in every way imaginable” in a “war without pity.”22 Prioritizing swift cavalry tactics, the Mexican guerrillas assaulted both Scott’s and Taylor’s lines of communication in an attempt to isolate occupying garrisons. When both generals responded by recruiting mounted Texas Ranger regiments to counter the elusive resistance, the war became a bitter contest over which side could outwait the other’s political tolerance for the costs of large-scale occupation and the atrocities that inevitably occurred.23
Throughout 1847, as the U.S. Army maintained a fragile hold on the Mexican interior, the U.S. Navy, Marine Corps, and Revenue Cutter Service performed a vital role in both sustaining the sprawling land occupation and expanding maritime pressure along the Pacific and Atlantic coasts. The Home Squadron, now under command of Commodore Matthew Perry, seized the Gulf towns of Alvarado and Tuxpan in April and then formed a 1,173-strong “Naval Brigade” to finally capture the holdout port of Tabasco in June. As before, Revenue Cutters provided valuable shallow-water capability for upriver naval expeditions while Marine detachments, with Sailor augmentation, supplied assault capability to oust the remaining Mexican garrisons.24
To the west, the Pacific Squadron likewise pressed forward to increase maritime pressure on the beleaguered Mexican government. This campaign unfolded as a series of blockades and offensives against Mazatlán, Mexico’s largest Pacific port, and sporadic attempts to neutralize military garrisons along Baja California. Employing the newly arrived 1st Regiment of New York Volunteers as reinforcements, the squadron seized, and sometimes lost, control over coastal cities such as San José del Cabo, La Paz, Guaymas, San Blas, and Todos Santos. Although the blockade suffered from logistical issues and Mexican counterattacks, the campaign succeeded in creating additional dilemmas for the Mexican national leadership and, more important, protected American gains in Alto California.25
The combined efforts of the U.S. military across Mexico, reflecting the first large-scale joint operations in American history, finally compelled the Mexican government to sign the Treaty of Guadalupe Hidalgo on February 2, 1848. With their northern provinces, capital region, and major ports under seemingly permanent occupation, and other regions such as Zacualtipán and the Yucatan now rising in rebellion, the Mexican leadership ceded rights to Texas and sold its vast northern provinces to the United States for a price of $15 million—less than half the amount Polk had offered prior to the war. In a historical irony, the U.S. military’s final action in Mexico was to reconstitute and rearm the broken Mexican army so that Mexico City could restore stability and enforce the new borders.26
Insights for Joint Warfare
The U.S. military’s decisive victory in the Mexican-American War stemmed, in part, from a forward-thinking approach to conducting joint operations across an expansive and multitheater contest. Throughout the controversial conflict, the U.S. Army, Marine Corps, Navy, and Revenue Cutter Service joined mostly complementary, though sometimes counterproductive, efforts across land and maritime domains to project and sustain expeditions of a continental scale. As now mandated in Joint Publication 3-0, Joint Operations, American military forces in that era—in the absence of codified joint doctrine and prior joint experience—improvised partnerships to leverage the “synergy” created by “the integration and synchronization of military operations in time, space, and purpose.”27
This convergence of land and maritime efforts proved critical in allowing the United States not only to win a sequence of decisive set-piece battles against the larger Mexican army but also to sustain the broader war effort long enough to compel the Mexican government to concede defeat. Without the U.S. Navy’s ability to neutralize the Mexican fleet, secure sea lines of communication, provide combat power to land engagements, and expand the blockade along both oceanic coasts, the U.S. Army would have faced significant—and potentially debilitating—challenges in translating battlefield victories into enduring gains. The resulting capacity to extend and expand landpower into early 1848 ultimately empowered the Polk administration’s negotiation position and led to the achievement of policy aims.
This increase in fighting capacity benefited from a significant wartime expansion of the relatively small U.S. military establishment to meet operational requirements. While the U.S. Army grew from an authorized strength of 8,613 Soldiers to 30,954 Regulars and 73,776 volunteers, the Marine Corps increased from 1,263 men scattered across ship-based detachments to create a full-size infantry regiment to fight in the land campaigns.28 The U.S. Navy, now authorized to increase to 11,000 Sailors, added personnel to man its dramatically expanded fleet, which resulted from both newly constructed ships and captured Mexican vessels. This rapid wartime growth, which also required a heavy reliance on civilian contract support in the form of merchants and teamsters, made a more robust joint concept possible and allowed an increase in American ability to mass forces and maintain operational endurance.
Another insight from this war centers on the importance of unity of command and shared vision. In the turbulent California Campaign, leaders from different Services arrived with uncoordinated operational approaches and lacked an agreed-upon plan for an efficient transition to postconflict governance. This absence led Stockton and Kearny to suffer initial defeats in detail after failing to synchronize their converging maritime and land offensives. When they recovered and finally defeated the Californios with a joint offensive, the egotistical commanders fell into acrimonious disputes over who would lead the consolidation of gains. Bitter disagreements over control of militia then further undermined unity of command and threatened to destabilize the new U.S. territory.
If the California effort stands as a cautionary lesson, the much larger expedition to seize Veracruz the next year remains a model for jointness. In that campaign, Scott’s central idea to create “further brilliant victories on a single line of operations toward the capital,” while “aided by the blockading squadron off the coast,” established a clear, unified operational approach.29 Throughout the operation, the involved Army and Navy leadership recognized Scott’s seniority, conducted collaborative planning prior to execution, reinforced the landing parties with naval firepower, and transitioned to agreed-upon roles following the city’s surrender. This successful “integration” of “joint functions,” as described by modern U.S. doctrine, established conditions for a successful march on Mexico City.30
In the final analysis, the performance of the U.S. military in the Mexican-American War instituted a fundamental and enduring precedent for the modern American way of war. The unified efforts of the U.S. Army, Marine Corps, Navy, and Revenue Cutter Service from 1846 to 1848 established inter-Service cooperation as a cornerstone of future U.S. expeditionary campaigns. In historic terms, the victory catapulted the United States into the position of dominant power in North America and set conditions for global expansion in the 20th century. Though still controversial in origin and outcome, the U.S. military’s performance in Mexico—across both the land and maritime domains and despite unprecedented requirements for joint cooperation—remains an important achievement in the history of American arms. JFQ
1 K. Jack Bauer, The Mexican War, 1846–1848 (Lincoln: University of Nebraska Press, 1992), 399.
2 See Richard Bruce Winders, Mr. Polk’s Army: the American Military Experience in the Mexican War (College Station: Texas A&M University Press, 1997); K. Jack Bauer, Surfboats and Horse Marines: U.S. Naval Operations in the Mexican War, 1846–48 (Annapolis: United States Naval Institute, 1969); Gabrielle M. Neufeld Santelli, Marines in the Mexican War, Occasional Paper Series, ed. Charles R. Smith (Washington, DC: Headquarters U.S. Marine Corps, 1991); and Robert Jay Lloyd, “Serving in Obscurity: United States Revenue Cutter Service Operations in the Gulf of Mexico During the Mexican American War, 1846–1847” (master’s thesis, New Mexico State University, 2007) for studies on individual Service contributions.
3 Joint Publication (JP) 3-0, Joint Operations (Washington, DC: The Joint Staff, January 17, 2017), I-2.
4 Bauer, The Mexican War, 194–195.
5 House Executive Document 60, Messages of the President of the United States, with the Correspondence, Therewith Communicated, Between the Secretary of War and Other Officers of the Government, on the Subject of the Mexican War, 30th Cong., 1st sess. (Washington, DC: Wendell and Van Benthuysen, 1848), 1268–1269.
6 Lloyd, “Serving in Obscurity,” 24–26; Santelli, Marines in the Mexican War, 3; Stephen A. Carney, Guns Along the Rio Grande: Palo Alto and Resaca de la Palma, CMH Pub. 73-2 (Washington, DC: U.S. Army Center of Military History, 2005), 6.
7 William A. DePalo, Jr., The Mexican National Army, 1822–1852 (College Station: Texas A&M University Press, 1997), 96.
8 Lloyd, “Serving in Obscurity,” 32.
9 Carney, Guns Along the Rio Grande, 5, 11–13.
10 Bauer, The Mexican War, 54–57, 90–100.
11 Lloyd, “Serving in Obscurity,” 40–49.
12 Bauer, Surfboats and Horse Marines, 165–166, 174–176.
13 Winston Groom, Kearny’s March: The Epic Creation of the American West, 1846–1847 (New York: Vintage Books, 2012), 202–212.
14 Ibid., 223–226.
15 Bauer, Surfboats and Horse Marines, 202–204.
16 Stephen A. Carney, Desperate Stand: The Battle of Buena Vista, CMH Pub. 73-4 (Washington, DC: U.S. Army Center of Military History, 2008), 35–39.
17 House Executive Document 60, 1271.
18 Bauer, Surfboats and Horse Marines, 70–74, 79–82.
19 Ibid., 82; Bauer, The Mexican War, 245–253.
20 Timothy D. Johnson, A Gallant Little Army: The Mexico City Campaign (Lawrence: University of Kansas Press, 2007), 84–97, 140, 239–241.
21 Santelli, Marines in the Mexican War, 38–43.
22 J. Jacob Oswandel, Notes of the Mexican War, 1846–1848, ed. Timothy D. Johnson and Nathaniel Cheairs Hughes, Jr. (Knoxville: University of Tennessee Press, 2010), 78.
23 Nathan A. Jennings, Riding for the Lone Star: Frontier Cavalry and the Texas Way of War, 1822–1865 (Denton: University of North Texas Press, 2016), 214–216, 230–232.
24 Bauer, Surfboats and Horse Marines, 101–105, 117–121; Lloyd, “Serving in Obscurity,” 75–82.
25 Bauer, Surfboats and Horse Marines, 207–219, 222–233.
26 Irving W. Levinson, Wars Within War: Mexican Guerrillas, Domestic Elites, and the United States of America, 1846–1848 (Fort Worth: Texas Christian University Press, 2005), 98–99, 109–110.
27 JP 3-0, I-1.
28 Winders, Mr. Polk’s Army, 72; Santelli, Marines in the Mexican War, 3, 34.
29 House Executive Document 60, 1271.
30 JP 3-0, I-1.