American annexation of Texas eventually sparked war with Mexico

How the US took half of Mexico

In just two years, the United States redrew the map of North America. Sparked by border disputes in Texas and fueled by President James Polk’s drive for expansion, the Mexican–American War (1846–1848) reshaped both nations.

Learn how Mexico’s anti-slavery stance shaped the US–Texas conflict

Historian Alice Baumgartner explores how Mexico’s abolition of slavery clashed with Anglo settlers' ambitions in Texas. The episode reveals how enslaved people fled south to freedom, reshaping the politics that led to Texas independence and the Mexican-American War.

Support for slavery helped drive Texas to revolt against Mexico

Mexico abolished slavery in 1829, but many Anglo-American settlers in Texas brought enslaved people and refused to comply. Their desire to preserve slavery was a major factor in Texas’s 1836 rebellion and independence from Mexico.

President Polk deliberately provoked war with Mexico

After Mexico refused to sell California and New Mexico, President James K. Polk ordered US troops into disputed territory between the Nueces River and the Rio Grande—knowing it would likely spark a conflict. When fighting broke out, he used it to justify declaring war.

Mexico’s political chaos weakened its defense against US invasion

Mexico’s post-independence instability—marked by coups, power struggles, and weak central control—left its northern frontier vulnerable. That political fragmentation shaped Mexico’s unpreparedness during the Mexican-American War and helped enable US conquest.

The US won every major battle of the Mexican-American War

Despite being outnumbered in key engagements, US forces defeated Mexican armies across every major front. Superior training, leadership, and logistics allowed the US to win decisively—capturing Mexico City without losing a single major battle.

Manifest destiny fueled US aggression against Mexico

The belief that the United States had a divine right to expand westward—known as manifest destiny—justified President Polk’s push for territorial conquest. It shaped public support for the Mexican-American War and framed the invasion as national destiny.

The US Army inherited the Apache Wars after the Mexican-American War

The resolution of the Mexican-American War inserted the US Army into an ongoing conflict between Apache groups and outside powers—transforming local resistance into a decades-long struggle against American expansion known as the Apache Wars.

The Compromise of 1850 tried to settle disputes over land gained from Mexico

Territory acquired in the Mexican-American War reignited fierce debates over slavery’s expansion. The Compromise of 1850 aimed to ease tensions by admitting California as a free state and letting other territories decide the issue—but the compromise ultimately failed and helped pave the way to the Civil War.

The Treaty of Guadalupe Hidalgo forced Mexico to surrender over half its territory

Signed in 1848, the Treaty of Guadalupe Hidalgo ended the war but came at a steep cost for Mexico—ceding 55% of its territory, including California and the Southwest, in exchange for $15 million and vague promises to protect Mexican residents.

Zachary Taylor became a national hero during the Mexican-American War

General Zachary Taylor led US forces to key victories in northern Mexico, earning widespread fame for his leadership. His popularity from the war propelled him to the presidency in 1848.

Mexico admired Lincoln for opposing the war and supporting Mexican sovereignty

As a congressman, Abraham Lincoln condemned the Mexican-American War as unjust. Years later, as president, he backed Mexico’s fight against French occupation. His principled stance earned enduring respect and monuments across Mexico.

US troops committed widespread atrocities during the Mexican-American War

American volunteer regiments frequently looted towns, raped civilians, and executed prisoners—especially in occupied northern Mexico. Historians have documented how racial hatred and impunity fueled war crimes that were rarely punished by military leadership.

The Mexican-American War led to the birth of the Associated Press

To cover the distant war efficiently, rival New York newspapers pooled resources to share reports from the front—forming what became the Associated Press. The war marked a turning point in how Americans received real-time news about foreign conflicts.

How the US entered WWI in 1917

Originally taking a position of neutrality during the course of World War I, the United States of America eventually relented. Entering the war in 1917, support for the British and French had risen and Americans were incensed by Germany's overtures to Mexico and U-boat attacks that sank ships and ended American lives. See how and why the US entered WWI in this article.

US westward expansion—and the status of slavery in the new territories—was a major cause of the American Civil War

The addition of new western lands forced the nation to confront whether slavery would spread beyond the South. Each debate over the admission of a new state sharpened the divide between free and slaveholding regions.

The Mexican-American War trained future Civil War generals

Many key military leaders of the Civil War—including Ulysses S. Grant, Robert E. Lee, and Thomas “Stonewall” Jackson—first saw combat in the Mexican-American War, gaining battlefield experience that shaped their later commands.

Irish immigrants deserted the US Army to fight for Mexico

During the Mexican-American War, hundreds of Irish Catholic immigrants—facing discrimination in the US Army—defected to Mexico and formed the Saint Patrick’s Battalion. Though many were captured and executed, they remain honored as heroes in Mexico.

Future President Abraham Lincoln challenged Polk’s justification for war with Mexico

As a freshman congressman, Abraham Lincoln introduced the “Spot Resolutions,” demanding President Polk prove that Mexico had attacked on US soil. This constituted Lincoln’s first major political stand and highlighted growing dissent over the war.

Some historians claim that Mexico's victory at Puebla may have prevented France from arming the Confederacy

According to some experts, Napoleon III planned to ship weapons from Mexico to Confederate forces to break the Union naval blockade. The delay caused by the Battle of Puebla meant French resources didn't reach the Texas border until after the Union Army's decisive victory at Vicksburg.

France, Spain, and Britain formed a joint military alliance to force Mexico to repay its debts

In October 1861, the three powers signed the Convention of London and landed troops at Veracruz that December. Britain and Spain reached settlements with Mexico and withdrew. France refused and aimed to change the regime in power in Mexico.

The 1783 peace treaty with Britain formally ended the Revolutionary War and nearly doubled the size of the United States.

Explore the social and cultural history of the Mexican-American War

Historian Peter Guardino joins host Don Wildman to explore how the war shaped ordinary lives on both sides of the border. Drawing from The Dead March, the episode reveals how culture, class, and ideology shaped the conflict and its consequences.

US military professionalism gave America a decisive edge in the war

The professionalism and engineering expertise of West Point–trained officers—like Grant, Lee, and Meade—gave the US a major advantage in the Mexican-American War, helping them win every major battle.

A wave of Latin American independence movements most likely prompted the Monroe Doctrine

Between 1810 and 1822, many Latin American colonies separated from Spanish rule, 10 in the last two years. Concerns that Spain and its European allies might try to regain these republics were a main reason behind Monroe's declaration.

Congress has formally declared war 11 times across five conflicts, the last in 1942

The five declared wars were the War of 1812, the Mexican-American War, the Spanish-American War, World War I, and World War II. Every major American military conflict since Korea, Vietnam, Iraq, and Afghanistan has been fought without a formal declaration.

France invaded Mexico to install a puppet monarchy and recover debt

Napoleon III used Mexico's default on foreign loans as cover for a larger imperial ambition: overthrowing President Benito Juárez's government and installing a French-backed monarchy. The Mexican army's surprise victory at Puebla helped delay those plans by nearly a year.

See the path Spanish conquistadors took to conquer the Aztecs

Spanish expeditions reached central Mexico as the Aztec Empire was expanding its influence. After securing bases in the Caribbean, they advanced west into Aztec territory, triggering a cascading conflict depicted in this interactive map and timeline.

The Declaration of Independence was not only a statement of principles but also an appeal for military allies that the struggling colonists needed to survive.

Cinco de Mayo holiday celebrations originated with California's Mexican Americans during the Civil War

California Latinos first celebrated Cinco de Mayo in 1862 through patriotic assemblies called Juntas Patrióticas. Ardent Union supporters, these individuals saw the Puebla victory as a win for democracy against both French imperialism and the Confederate cause.

The origins and growth of the Juneteenth holiday

The American holiday of Juneteenth celebrates the emancipation of African American slaves, a process which unfolded over the four years of the Civil War and several months afterward. June 19 took on special significance as the day Union officials proclaimed slaves free in Texas in 1865, the last holdout after the Civil War ended. Roughly 4 million people were freed from slavery as a result of emancipation. Read this brief article summarizing the holiday's development.

Japan's imperial expansion in Asia in the 1930s set the stage for war with the US.

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The Monroe Doctrine helped lead to the American occupation of territory abroad

This podcast explores how the policy motivated a century of US military intervention throughout Latin America, the Caribbean, and the Pacific—covering the annexation of Hawaii, the Spanish-American War, and occupations of Cuba, Haiti, and Panama.

Hitler declared war on the United States four days after Pearl Harbor

Despite having no treaty obligation to join Japan’s fight, Hitler declared war on the US on Dec. 11, 1941. The move pulled America into the European theater and is widely seen as one of Hitler’s most strategic blunders.

The first test of America's war powers came just a decade after the Constitution was ratified

During the undeclared Quasi-War with France in 1800, the Supreme Court ruled in Bas v. Tingy that Congress had authorized a valid "imperfect war" through statutes alone, without a formal declaration, establishing that there is a legal spectrum between peace and declared war.

Juneteenth celebrates the day that the last enslaved people were notified of the Emancipation Proclamation, 2 years after it was signed.

The Kansas-Nebraska Act sparked violence that foreshadowed the Civil War

The 1854 Kansas-Nebraska Act let settlers vote on whether to allow slavery, repealing the Missouri Compromise. Competing proslavery and antislavery groups poured into Kansas, sparking years of bloody conflict known as "Bleeding Kansas."

Mexican Independence Day is celebrated on September 16

Cinco de Mayo is widely mistaken for Mexican Independence Day. September 16 is the actual date, commemorating the 1810 Grito de Dolores, Father Miguel Hidalgo's call to revolution that launched Mexico's war against Spanish colonial rule.

Madison was America's first president during a formally declared war

During James Madison's presidency, Congress formally declared war on Britain in 1812 over its practice of seizing American sailors, trade restrictions, and repeated violations of US sovereignty—marking the first time a sitting American president led the nation through a declared war.

Should the US have entered into World War I?

America entered World War I in 1917, but had remained neutral until that point. President Woodrow Wilson addressed Congress, further underlining the USA's neutrality. Eleven weeks later, he asked for a declaration of war. With attacks by German saboteurs on an American munitions depot, it seemed he had no choice. But did he? This article asks what might have happened if the US stayed out of WWI.

Tex-Mex is its own distinct cuisine with roots in the Texas borderlands

The cuisine emerged from Tejano cooking, blending northern Mexican ranch food with ingredients such as yellow cheese, beef, and wheat flour. Dishes now considered staples, including chili con carne and fajitas, were Tex-Mex inventions rather than traditional Mexican dishes.

Discover why Texas runs its own electric grid, separate from the other US interconnections

In 1935, electrical utilities in the Lone Star State opted to rely on the state's own fossil fuel reserves to power an independent electric grid. While this prevented the federal oversight required for the Eastern and Western Interconnections that span multiple states, it also meant Texas's grid was unable to draw sufficient backup power during the winter 2021 power grid failure.

Foreign policy and war defined Madison's presidency

During James Madison's presidency, disputes with Britain and France over trade, maritime rights, and impressment dominated foreign policy, culminating in the War of 1812 and shaping how the United States engaged with major European powers.

Thoreau's 'Civil Disobedience' was largely a protest against the Mexican-American War

Henry David Thoreau refused to pay taxes that funded what he saw as an unjust war waged to expand slavery. His act of protest inspired his famous essay "Civil Disobedience," a foundational text for nonviolent resistance.

Why Cinco de Mayo is more popular in the US than Mexico

Many in the United States believe Cinco de Mayo (celebrated annually on May 5) is Mexico's equivalent of the Fourth of July, but that's a common misconception: The holiday commemorates a battle in the fight for independence rather than the day Mexico declared independence. Interestingly, the holiday is more celebrated in the US than in Mexico, largely thanks to the Chicano Movement of the 1960s and 1970s.

Abraham Lincoln's victory in 1860 sparked Southern secession—even before his inauguration

Abraham Lincoln's election on an antislavery expansion platform convinced many Southerners that their way of life was under threat. Within three months, seven states seceded from the Union—forming the Confederacy—before Lincoln took office in March 1861.

The Aztec Empire began as a three-city military alliance

The Aztec Empire emerged in 1428 when Tenochtitlan, Texcoco, and Tlacopan formed the Triple Alliance, combining military power and tribute networks. This pact transformed the three city-states into a dominant regional empire that rapidly expanded across central Mexico.

The Roosevelt Corollary transformed the Monroe Doctrine from a defensive warning into a rationale for US military intervention

In 1904, President Theodore Roosevelt declared that the US had the right to exercise international police power in Latin America. Over the following two decades, the US intervened militarily in the region about a dozen times—often enough that Marines became known locally as "State Department troops."

The US never formally declared war in Vietnam

Instead of formally declaring war, Congress passed the Gulf of Tonkin Resolution in 1964, granting President Johnson broad authority to use military force. The resolution became the legal basis for escalating US involvement without an official declaration of war.

The Civil War turned the Continental Divide into an American symbol of identity

Historians argue that the boundary only became a celebrated American symbol in the 1860s, when Civil War-era leaders promoted a west-east geographic divide to replace the devastating north-south political divide, and that the term's use spiked after the transcontinental railroad crossed it in 1868.