Mexican-American War 1846-1848: Justified or Not? — Reading Comprehension

The Mexican-American War of 1846 to 1848 was a turning point in the history of North America. The United States and Mexico fought over land, power, and national identity. To understand whether the war was justified, historians compare the goals, actions, and beliefs of people on both sides, as well as the long-term consequences.

The causes of the war are complex. In the early 1800s, many Americans believed in Manifest Destiny—the idea that the United States was meant to expand across the continent. This belief encouraged settlers to move west and fueled political pressure to acquire new territories. At the same time, Mexico controlled a vast region, including present-day Texas, California, and New Mexico. The U.S. annexation of Texas in 1845 upset Mexican leaders, who saw it as an illegal seizure of their land. Disagreements about the border between Texas and Mexico—especially the Rio Grande—escalated tensions.

President James K. Polk, a strong supporter of Manifest Destiny, sent U.S. troops to the disputed territory. Mexico viewed this as an invasion. Fighting broke out in April 1846. In a message to Congress, Polk declared, “Mexico has passed the boundary of the United States, has invaded our territory and shed American blood upon American soil.” This statement was used as justification for war, but many Americans questioned its truth. Was the land truly U.S. soil, or was it still part of Mexico?

Supporters of the war argued that the United States had the right to protect its citizens and claim land they believed was rightfully theirs. They saw expansion as a way to spread democracy and economic opportunity. However, critics, including Congressman Abraham Lincoln, challenged the official story. Lincoln demanded to know the exact spot where blood had been shed, suggesting Polk had provoked the conflict. Another critic, Henry David Thoreau, protested the war by refusing to pay taxes, stating, “I cannot for an instant recognize that political organization as my government which is the slave’s government also.” Thoreau’s words showed how the war was connected to debates about slavery and justice.

The Mexican perspective was shaped by national pride and the defense of their territory. Mexican leaders viewed the U.S. as an aggressive neighbor using its military power to take land. For Mexico, the war was a fight to preserve sovereignty and dignity. Many Mexican citizens suffered as battles destroyed towns and disrupted daily life. The outcome of the war was disastrous for Mexico. The Treaty of Guadalupe Hidalgo, signed in 1848, forced Mexico to give up nearly half its land—including California and the Southwest—to the United States in exchange for $15 million.

The consequences of the war were far-reaching. The United States gained vast new territories, fulfilling the dream of Manifest Destiny. However, the war also deepened divisions over slavery, as Americans argued about whether new states would permit enslaved labor. For Mexico, the loss of territory was a national tragedy, leading to political instability and bitterness toward the U.S. The war also set a precedent for using military force to achieve political goals.

Historians continue to debate whether the Mexican-American War was justified. Some argue that expansion was inevitable and beneficial for the U.S., while others point out the injustice and violence inflicted on Mexico. By examining the evidence and considering multiple perspectives, we can better understand the complexity of this controversial conflict.

Interesting Fact: The Mexican-American War was the first U.S. war to be covered by newspaper reporters from the battlefield, giving Americans back home new insights into the realities of war.

When did the Mexican-American War start?

What river was a disputed border?

Which treaty ended the war?

What idea encouraged U.S. expansion?

Why did Abraham Lincoln question the war?

What did Mexico lose after the war?

The war lasted from 1846 to 1848.

What does 'annexation' mean?