Constitution Daily

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The war that triggered the Civil War

May 16, 2012 by Scott Bomboy


Mid-May marks two key anniversaries in the conflict between the United States and Mexico in 1846 that set in motion the Civil War – and led to California, Texas and eight other states joining the Union.

On May 13, 1846, the United States Congress declared war on Mexico after a request from President James Knox Polk. Then, on May 26, 1848, both sides ratified the peace treaty that ended the conflict.

In between those dates was enough drama to last for generations and the appearance of some familiar names that would dominate the Civil War, from Abraham Lincoln to General Robert E. Lee.

To save space and make a long story short, the conflict centered on the independent republic of Texas, which opted to join the United States after establishing its independence from Mexico a decade earlier.

Mexico considered that an act of war, and after border skirmishes, President Polk asked for the war declaration, since in the Constitution, only Congress can declare a war (as in Article I, Section 8).

In the fighting that followed, the mostly volunteer United States military secured control of Mexico after a series of battles, and the Treaty of Guadalupe Hidalgo was signed on February 2, 1848.

The pact set a border between Texas and Mexico, and ceded  California, Nevada, Utah, New Mexico, most of Arizona and Colorado, and parts of Oklahoma, Kansas, and Wyoming to the United States.

In today’s terms, those 10 states account for 136 electoral votes, more than half of the votes needed to secure a win in a presidential election.

It also cut the territorial size of Mexico in half.

One underlying issue behind the war was slavery, and how addition of states and territories would alter the balance between free and slave states.

The Missouri Compromise of 1850 attempted to appease Southern concerns about the shifting balances, but the die was cast as the nation headed toward the Civil War in 1861.

The Treaty of Guadalupe Hidalgo also set in motion a whole range of issues for Mexican-Americans and Native Americans.

During the conflict, one of the vocal objectors in the Whip party was Rep. Abraham Lincoln from Illinois. Key players on the political side included Jefferson Davis and Stephen Douglas.

On the battlefield, Robert E. Lee, Ulysses S. Grant and Stonewall Jackson were among the dozens of commanders who would later emerge in the Civil War.

Scott Bomboy is the editor-in-chief of Constitution Daily.


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