21 JUN--This Day in US Military History

1916 – The controversial U.S. military expedition against Mexican revolutionary Pancho Villa brings the United States and Mexico closer to war when Mexican government troops attack U.S. Brigadier General John J. Pershing’s force at Carrizal, Mexico.

The Americans suffered 22 casualties, and more than 30 Mexicans were killed. Against the protests of Venustiano Carranza’s government, Pershing had been penetrating deep into Mexico in pursuit of Pancho Villa. After routing the small Mexican force at Carrizal, the U.S. expedition continued on its southern course.
In 1914, following the resignation of Mexican leader Victoriano Huerta, Pancho Villa and his former revolutionary ally Venustiano Carranza battled each other in a struggle for succession. By the end of 1915, Villa had been driven north into the mountains, and the U.S. government recognized General Carranza as the president of Mexico. In January 1916, to protest President Woodrow Wilson’s support for Carranza, Villa executed 16 U.S. citizens at Santa Isabel in northern Mexico. Then, on March 9, he ordered a raid on the border town of Columbus, New Mexico, in which 17 Americans were killed and the center of town was burned. Cavalry from the nearby Camp Furlong U.S. Army outpost pursued the Mexicans, killing several dozen rebels on U.S. soil and in Mexico before turning back.
On March 15, under orders from President Wilson, U.S. Brigadier General John J. Pershing launched a punitive expedition into Mexico to capture or kill Villa and disperse his rebels. The expedition eventually involved some 10,000 U.S. troops and personnel. It was the first U.S. military operation to employ mechanized vehicles, including automobiles and airplanes.
For 11 months, Pershing failed to capture the elusive revolutionary, who was aided by his intimate knowledge of the terrain of northern Mexico and his popular support from the people there. Meanwhile, resentment over the U.S. intrusion into Mexican territory led to a diplomatic crisis with the government in Mexico City.
On June 21, the crisis escalated into violence when Mexican government troops attacked a detachment of the 10th Cavalry at Carrizal. If not for the critical situation in Europe, war might have been declared.
In January 1917, having failed in their mission to capture Villa, and under continued pressure from the Mexican government, the Americans were ordered home. Pancho Villa continued his guerrilla activities in northern Mexico until Adolfo de la Huerta took over the government and drafted a reformist constitution. Villa entered into an amicable agreement with Huerta and agreed to retire from politics. In 1920, the government pardoned Villa, but three years later he was assassinated at his ranch in Parral.

https://thisdayinusmilhist.wordpress.com/2005/06/21/june-21/