1846-1848: The US-Mexican War

The U.S.-Mexican War profoundly changed the history of both countries. It was the first foreign war fought by the US. It was fought almost entirely on what was at the time Mexican soil. For Mexico, the war was a national wound. Soon afterward both countries faced civil war.

Battle of Molino del Rey, US Mexican War. Lithograph by James Bailie, 1848.

The US suffered losses. More than 5,800 Americans were killed or wounded in battle, and 11,000 soldiers died from diseases. The enormous financial cost of the war exceeded $75 million, a nearly unimaginable cost at that time.

In the US these costs were justified by the doctrine of Manifest Destiny. The territorial conquest made the US a continental power with riches gained at Mexico’s expense. The US gained gold and silver deposits in California territories as well as ports on the Pacific coast. These new riches drove the expansion of the economy and a westward migration, but by upsetting the balance between free and slave states, the spoils of war with Mexico later raised the internal tensions that lead to the American Civil War.

Not all Americans agreed with the war with Mexico. In the summer of 1846 the writer Henry David Thoreau protested the war by refusing to pay his poll tax. He was thrown in jail in Concord MA. His friend Ralph Waldo Emerson who also disagreed with the war, but felt protest was futile, paid the tax and Thoreau was released. Two years later however Thoreau gave a lecture entitled “Resistance to Government” which was later printed as an essay that has inspired future generations of dissenters all over the world: “Civil Disobedience.”

For Mexico, the war was a series of tragedies. Apart from the loss of wealth and territory and the thousands of military and civilian deaths in battles, the war left tens of thousands of orphans, widows and cripples.

The war and subsequent defeat spawned political instability in Mexico and led to a new despotic regime and eventually to another civil war–the Mexican Revolution.

Mexicans continue to lament the consequences of the war that they call “the American Intervention.” It destroyed a sense of national honor, reduced Mexico’s land and wealth and it created understandably deep and long-lasting feelings of resentment toward “Yankees.”