On June 21, 1916, a detachment of the 10th Cavalry, under the command of Brigadier General John J. Pershing, was attacked by Mexican government troops at Carrizal, Mexico. The Americans suffered 22 casualties, and more than 30 Mexicans were killed.
Yet, the whole reason that Gen. Pershing and the US Army was on the expedition in Mexico was to capture or kill Mexican Revolutionary, Pancho Villa, for his raids on U.S. civilians; the Mexican government was also seeking Villa.
The mission was ordered by President Wilson in March of that year, it was the first US military operation to employ mechanized vehicles, including automobiles and airplanes.