Why historians believe Cinco de Mayo prevented the Confederacy's win in the Civil War

• French Emperor Napoleon III had planned to trade weapons for cotton with Confederate states during France's invasion of Mexico.
• However, Mexico's resolve at the Battle of Puebla in 1862 prevented France from supplying weapons to the Confederacy during the Civil War.

As people across the country indulge in Cinco De Mayo celebrations with margaritas and tacos, few may know about the connection the holiday has to US history.

On May 5, 1862, the Mexican army defeated the French in the Battle of Puebla. This prevented French Emperor Napoleon III from supplying weapons to the Confederacy during the Civil War. Napoleon III had planned to trade weapons for cotton with the Confederate states during France's invasion of Mexico. But upon arriving at combat, the French found that they were unprepared to battle the resolve of the Mexican army.

Emperor Napoleon III wanted to claim Mexico for France.

In 1860, Mexico was dealing with bankruptcy and told their European creditors that they would be pausing payments for two years while they got their affairs in order. That upset the French, Spanish, and British, so in 1861, the three countries sent their military forces to Mexico to collect their debts.

The British and the Spanish eventually settled the issue of debt, but France was not satisfied. Napoleon III wanted to make Mexico a colony of France. Spanish and British forces eventually withdrew from Mexico once Napoleon III's ambitious plans were made known. Knowing he wouldn't face any resistance from the other European forces and that the US was in the midst of the American-Native Wars and the Civil War, he decided to press on.

In 1862, French General Charles de Lorencez marched his forces into the port city of Veracruz with the goal of capturing Mexico City. However, on May 5th, French forces were decimated at Puebla at the hands of Mexican General Ignacio Zaragoza and his troops.

Losing at the Battle of Puebla forced French forces to delay their weapons trade with the Confederacy.

The French retreated to Veracruz where they stayed put for over a year.

That decision has led some historians to believe France's year-long delay to go back into combat gave the Union Army time to rack up enough victories against the Confederacy before Napoleon could send artillery and ammunition.

However, others believe that the Battle of Gettysburg was about to begin at the time of France's retreat and that the Union Army was already in a good position to wrap up the war by year's end.

"Even if French were able to set their supply lines by mid-1863, it would have made very little difference in the outcome of the Civil War," Eric Rojo, a retired U.S. Army Colonel and commander-in-chief of the Military Order of the Loyal Legion of the United States, an organization composed of descendants of Union officers in the Civil War, told History.com.

President Abraham Lincoln issued the Emancipation Proclamation on January 1, 1863 freeing enslaved Black people.

Mexican Americans living in California at the time saw the connection between the Union army's victory and the Battle of Puebla as a fight against slavery. Before the state became a part of the US, many Mexicans who lived in California voiced their opposition to slavery as early as 1829. Once the Mexican army prevailed, according to WBUR, they celebrated with fireworks and drinks, and thus, Cinco de Mayo was born.