In the pre-dawn hours of March 16, 1916, a Mexican army under the command of Pancho Villa crossed the border and attacked Columbus, New Mexico. This event still stands as the last invasion of the continental United States by a foreign power since the War of 1816.
Villa himself waited outside the town, perhaps over the border. Four Villista Divisions, about 500 men, attacked in the darkness, yelling and shooting at anyone they saw, setting fire to the town.
The Mexicans made several mistakes. When they attacked the army post north of town, they mistook the stables for the barracks and killed only horses. They set fire to the Commercial Hotel, and by the light of that blaze, U.S. soldiers could recognize their targets. After two hours, the Mexican bugler sounded retreat, and the attack ended. Seventeen Americans died. So did about 100 Mexican soldiers.
Why did he do it? (Later, he claimed no knowledge of the raid). Villa was mad at the U.S. for supporting the Carranza government. The U.S. had an arms embargo. And conspiracy theories – Did the German Government pay Villa? Was he angry at a Columbus merchant who took his money and then withheld his goods? And so forth.
The result – Gen. Pershing invaded Mexico. He didn’t catch Villa, but gained experience in mechanized warfare (including airplanes), experience that helped him later, in the European theater.