war between the United States and Mexico had two basic causes.
First, the desire of the U.S. to expand across the North American
continent, the policy of Manifest Destiny, to the Pacific Ocean
caused conflict with all of the U.S. neighbors; from the British
in Canada and Oregon to the Mexicans in the southwest and, of course,
with the Native Americans, many on U.S. treaty secured lands.
The second basic cause of the war with Mexico was the Texas War
of Independence and the subsequent annexation of that area to the
the beginning of hostilities, the U.S. military reported to the
President and it became apparent to the Polk Administration that
only a complete battlefield victory would end the war. Continued
fighting in the dry deserts of northern Mexico convinced the United
States that an overland expedition to capture of the enemy capital,
Mexico City, would be hazardous and difficult. To this end, General
Winfield Scott proposed what would become the largest amphibious
landing in history, (at that time), and a campaign to seize the
capital of Mexico. The Marine Corps still recognizes this landing
in the first line of the Corps' hymn: From the Halls of Montezuma.
interesting aspect of the war involves the fate of U.S. Army deserters
of Irish origin who joined the Mexican Army as the Batallón
San Patricio (Saint Patrick's Battalion). This group of Catholic
Irish immigrants rebelled at the abusive treatment by Protestant,
American-born officers and at the treatment of the Catholic Mexican
population by the U.S. Army. At this time in American history, Catholics
were an ill-treated minority, and the Irish were an unwanted ethnic
group in the United States. In September 1847, the U.S. Army hanged
sixteen surviving members of the San Patricios as traitors. To this
day, they are considered heroes in Mexico.
story of this famed group begins with the founder and chief conspirator,
John Riley, a Galway native born in 1817. Riley deserted from the
British army while stationed in Canada and went to Michigan, where
he later enlisted in the US Army in 1845. He was able to defect
to the Mexican Army when his commander granted him permission to
cross into Mexico to attend mass. It was there, in Matamoros, Riley
joined the Mexican Army as a lieutenant, which resulted in his pay
rising from seven dollars per month to 57 dollars per month. While
desertion from the US armed forces was punishable by death, Riley
was not deterred in capitalizing on the dis-satisfaction of many
Irish-born US soldiers with their adopted country. Aided by his
second-in-command, Patrick Dalton, who was from the parish of Tirawley,
near Ballina, County Mayo, Riley at first was successful in persuading
48 Irishmen to defect, and these men made up the original Saint
Patrick's Battalion. In addition to more Irishmen joining, they
welcomed other foreign-born US deserters, as well as American-born
deserters. Also, some Irish-born civilian residents of Mexico were
persuaded to join the struggle. Even when the number of San Patricios
rose to more than 200, Irish-born members still represented nearly
50 per cent.
back, to the motivation for the policy of Manifest Destiny, we need
to examine President Jefferson's acquisition of the right to treat
with the Indian Nations for land in Louisiana Territory in 1803,
Americans illegally migrated westward in ever increasing numbers,
very often into lands not belonging to the United States. By the
time President Polk came to office in 1845, this idea, based on
racist principals called "Manifest Destiny", had taken
root among the American people, and President Polk was a firm believer
in the idea of expansion. The belief that the U.S. basically had
a Euro-centered God-given right to occupy and "civilize"
the whole continent gained favor as more and more Americans invaded
the western lands. The fact that most of those areas already had
Tribal people living upon them was usually ignored, with the attitude
that democratic English-speaking America, with its high ideals and
Protestant Christian ethics, would do a better job of running things
than the Native Americans or Spanish-speaking Catholic Mexicans.
Destiny did not necessarily call for violent expansion if the land
can be bought cheap. In both 1835 and 1845, the United States offered
to purchase California from Mexico, for $5 million and $25 million,
respectively. The Mexican government refused the opportunity to
sell half of its country to Mexico's most dangerous neighbor. Many
Americans opposed what they called "Mister Polk's War."
Whig Party members and abolitionists in the North believed that
slave-owners and Southerners in Polk's administration had planned
the war. They believed the South wanted to win Mexican territory
for the purpose of spreading and strengthening slavery. This opposition
troubled President Polk. But he did not think the war would last
long. He thought the US could quickly force Mexico to sell him the
territory he wanted.
secretly sent a representative to former Mexican dictator Santa
Ana, who was living in exile in Cuba. Polk's representative said
the United States wanted to buy California and some other Mexican
territory. Santa Ana said he would agree to the sale, if the United
States would help him return to power. President Polk ordered the
US Navy to let Santa Ana return to Mexico. American ships that blocked
the port of Vera Cruz permitted the Mexican dictator to land there.
Once Santa Ana returned, he failed to honor his promises to Polk.
He refused to end the war and sell California. Instead, Santa Ana
organized an army to fight the United States.
all American westward migration was unwelcome. In the 1820's and
1830's, Mexico, newly independent from Spain, needed settlers in
the under-populated northern parts of the country. An invitation
was issued for people who would take an oath of allegiance to Mexico
and convert to Catholicism, the official religion. Thousands of
Americans took up the offer and moved, often with slaves, to the
Mexican province of Tejas (texas). Soon however, many of the new
"Texicans" or "Texians" were unhappy with the
way the government in Mexico City tried to run the province. In
1835, the Tejanos revolted, and after several bloody battles, the
Mexican President, Santa Anna, was forced to sign the Treaty of
Velasco in 1836 This treaty gave Tejas (texas) its independence,
but many Mexicans refused to accept the legality of this document,
as Santa Anna was a prisoner of the Tejanos at the time. The Republic
of Tejas (texas) and Mexico continued to engage in border fights
and many people in the United States openly sympathized with the
U.S.-born Texans in this conflict. As a result of the savage frontier
fighting, the American public developed a very negative stereotype
against the Mexican people and government. Partly due to the continued
hostilities with Mexico, Texas decided to join with the United States,
and on July 4, 1845, the annexation gained approval from the U.S.
Military campaign accounts: The "Army of Observation"
commanded by General Zachary Taylor was deployed to Corpus Christi,
at the mouth of the Nueces River, to protect newly annexed Texas
in the summer of 1845. The force consisted of 5 regiments of infantry,
1 regiment of dragoons, and 16 companies of artillery. After the
beginning of hostilities, the U.S. military embarked on a three-pronged
strategy designed to seize control of northern Mexico and force
an early peace. Two American armies moved south from Texas, while
a third force under Colonel Stephen Kearny travelled west to Sante
Fe, New Mexico and then to California. In a series of battles at
Palo Alto and Resaca de Palma (near current-day Brownsville, Texas),
the army of General Zachary Taylor defeated the Mexican forces and
began to move south after inflicting over a thousand casualties.
In July and August of 1846, the United States Navy seized Monterey
and Los Angeles in California. In September, 1846, Taylor's army
fought General Ampudia's forces for control of the northern Mexican
city of Monterey in a bloody three-day battle. Following the capture
of the city by the Americans, a temporary truce ensued which enabled
both armies to recover from the exhausting Battle of Monterey. During
this time, former President Santa Anna returned to Mexico from exile
and raised and trained a new army of over 20,000 men to oppose the
invaders. Despite the losses of huge tracts of land, and defeat
in several major battles, the Mexican government refused to make
March 9, 1847, General Scott landed with an army of 12,000 men on
the beaches near Veracruz, Mexico's most important eastern port
city. From this point, from March to August, Scott and Santa Anna
fought a series of bloody, hard-fought battles from the coast inland
toward Mexico City.
20 August 1847. Santa Anna promptly made another stand on Churubusco
where he suffered a disastrous defeat in which his total losses
for the day "killed, wounded, and especially deserters"
were probably as high as 10,000. Scott estimated the Mexican losses
at 4,297 killed and wounded, and he took 2,637 prisoners. Of 8,497
Americans engaged in the almost continuous battles of Contreras
and Churubusco, 131 were killed, 865 wounded, and about 40 missing.
proposed an armistice to discuss peace terms. Santa Anna quickly
agreed; but after two weeks of fruitless negotiations it became
apparent that the Mexicans were using the armistice merely for a
breathing spell. On 6 September Scott broke off discussions and
prepared to assault the capital. To do so, it was necessary to take
the citadel of Chapultepec, a massive stone fortress on top of a
hill about a mile outside the city proper. Defending Mexico City
were from 18,000 to 20,000 troops, and the Mexicans were confident
of victory, since it was known that Scott had barely 8,000 men and
was far from his base of supply.
del Rey, 8 September 1847. On 8 September 1847, the Americans launched
an assault on Molino del Rey, the most important outwork of Chapultepec.
It was taken after a bloody fight, in which the Mexicans suffered
an estimated 2,000 casualties and lost 700 as prisoners, while perhaps
as many as 2,000 deserted. The small American force had sustained
comparatively serious losses "124 killed and 582 wounded"
but they doggedly continued their attack on Chapultepec, which finally
fell on 13 September 1847. American losses were 138 killed and 673
wounded during the siege of the fortress. Mexican losses in killed,
wounded, and captured totaled about 1,800. The fall of the citadel
brought Mexican resistance practically to an end. Authorities in
Mexico City sent out a white flag on 14 September 1847. Santa Anna
abdicated the Presidency, and the last remnant of his army, about
1,500 volunteers, was completely defeated a few days later while
attempting to capture an American supply train.
On 2 February 1848, the Treaty of Guadalupe Hidalgo was signed,
ratified in the U.S. Senate on 10 March 1848, by the Mexican Congress
in May. The treaty called for the annexation of the northern portions
of Mexico to the United States. On 1 August 1848 the last American
soldier departed for home.
In return, the U.S. agreed to pay $15 million to Mexico as compensation
for the seized territory. This "seized Mexican territory"
is the most controversial issue in the Southwest history. Almost
never delineated is the actual territory controlled and not just
claimed by Mexico or previously by Spain.
bravery of the individual Mexican soldier goes a long way in explaining
the difficulty the U.S. had in conducting the war. Mexican military
leadership was often lacking, at least when compared to the American
leadership. And in many of the battles, the superior cannon of the
U.S. artillery divisions and the innovative tactics of their officers
turned the tide against the Mexicans. The war cost the United States
over $100 million, and ended the lives of 13,780 U.S. military personnel.
America had defeated its weaker and somewhat disorganized southern
neighbor, but not without paying a terrible price.
This divisive legacy is so often overlooked in our general education.
Despite early popularity at home, the war was marked by the growth
of a loud anti-war movement that included such noted Americans as
Ralph Waldo Emerson, former president John Quincy Adams and Henry
David Thoreau. The center of anti-war sentiment gravitated around
New England, and was directly connected to the movement to abolish
slavery. Texas became a slave state upon entry into the Union.
2. While it is widely perceived in Mexico that the San Patricios
defected solely on the issue of religion, this myth is examined
in a later chapter of Robert Miller's book: Shamrock and Sword,
entitled "Why they Defected". The fact that there was
rampant anti-Catholic bigotry in the US at that time does not play
as great a role in the formation of the unit as is believed in Mexico.
Miller states that the religious bond was not a main reason why
many defected. The attractive offer of high pay in the Mexican Army
and the promise of land grants to defectors after the war outweighed
the fraternal bond over religion, according to Miller.
main reason for their hero status in Mexico is derived from their
exemplary performance in the battlefield. The San Patricios ultimately
suffered severe casualties at the famous battle at Churubusco, which
is considered the Waterloo for the Mexican Army in this war. Mexican
President Antonio Lopez Santa Anna, who also commanded the armed
forces, stated afterwards that if he had commanded a few hundred
more men like the San Patricios, Mexico would have won that ill-famed
San Patricio soldier who deserted from the US side was interned
after the war in Mexico and subsequently given an individual court-martial
trial. Many of the Irish were set free, but some paid the ultimate
price. Roughly half of the San Patricio defectors who were executed
by the US for desertion were Irish. Those Irish who were released
by American authorities did not return to the US; some stayed in
Mexico while most returned to Ireland, including John Riley who,
surprisingly, was spared execution.
Miller makes it clear that the Irish deserters of the Saint Patrick's
Battalion were in no way representative of the Irish-born soldiers
who made up one-fourth of all enlisted men in the US Army during
the US-Mexican War. There were seventeen totally Irish companies
who saw action in this war; many were highly decorated units such
as the Emmet Guards from Albany, New York; the Jasper Greens of
Savannah, Georgia; the Mobile Volunteers of Alabama; the Pittsburgh
1959, the Mexican government dedicated a commemorative plaque to
the San Patricios across from San Jacinto Plaza in the Mexico City
suburb of San Angel; it lists the names of all members of the battalion
who lost their lives fighting for Mexico, either in battle or by
execution. There are ceremonies there twice a year, on September
12, this is the anniversary of the executions, and on Saint Patric's
Day. A major celebration was held there in 1983, when the Mexican
government authorized a special commemorative medallion honoring
the San Patricios.
Infantry flag made by the nuns at San Luis Potosi is described as
"The banner is of green silk, and on one side is a harp, surmounted
by the Mexican coat of arns, with a scroll on which is painted 'Lebertad
por Republica Mexicana". Underneath the harp is the motto "Erin
Go Bragh'. (Ireland Forever) On the other side is a painting made
to represent St. Patrick, his left hand a key and in his right a
crook or staff resting upon a serpent.
is the flag captured at Churubusco by the 14th US Infantry and later
apparently taken to West Point and placed in the chapel. But, it
did not survive because when President Truman returned the captured
Mexican War flags it was not returned. The chapel was replaced sometime
in the 1930's and by then the flag seems to have vanished.
In Mexico, a special day is remembered to celebrate the bravery
of the teenaged military cadets at the military academy at Chapultepec
Castle, which was attacked by Scott's army on September 13, 1847.
"Dia de Los Niños Heroes de Chapultepec" (day of
the boy heroes of Chapultepec), is commemorated every year on the
anniversary of the battle.
high on a hill, Chapultepec Castle had once been the resort of Aztec
princes, hence its fame as the Halls of Montezuma. Since 1833, it
had served as Mexico's military academy, and the cadets now fought
side by side with seasoned soldiers in heroic defense of their castle
and country. Six of the youths died, one clutching the Mexican flag
to keep it from American hands. For their valor, they have been
honored in annual celebrations as Los Niños Héroes.
Ordered to retreat by their Commandant, these young cadets joined
the fight- the boy heroes who are honored every year are the four
teenaged cadets (Francisco Marquez, the youngest, was thirteen years
old!) and their lieutenant squadron leader, Juan de la Barrera,
(the oldest, age 20), who lost their lives in that battle.
Kohn, George C. Dictionary of Wars. New York: Facts On File Publications.
Eisenhower, John S.D. So Far From God: The U.S. War With Mexico
1846-1848. New York: Anchor Books, Doubleday. 1989.
Winders, Richard Bruce. Mr. Polk's Army. Texas A&M, 1997.
Frazier, Donald S., ed. The U.S. and Mexico at War: Nineteenth Century
Expansionism and Conflict. Macmillan Library Reference, 1998.
Lee, R. "The History Guy: The Mexican-American War"
Miller, Robert R: Shamrock & Sword