What action by Pancho Villa spurred the U.S. to invade Mexico in 1916?

In 1916, the rebel leader Pancho Villa raided Columbus, New Mexico, and killed 18 people.

Villa opposed U.S. influence in Mexico and was seeking to overthrow the Mexican government.

In response, President Woodrow Wilson sent General John Pershing and 6,000 troops into northern Mexico on a mission to find Villa.

Pershing’s expedition clashed with Mexican troops but never caught up with Villa.