On January 28, 1917 the United States government gave up the search for Mexican revolutionary leader Pancho Villa. What is officially known in the United States as the "Mexican Expedition" started March 14, 1916 and involved 5,000 U.S military personnel lead by Major General John J. Pershing.
The tension with Pancho Villa started in 1915 when the U.S. sided with the Venustiano Carranza's government. As a result of this betrayal Pancho Villa and his troops started to attack U.S. targets in northern Mexico.
After a Villa-led attack on Columbus, New Mexico and defeating the U.S 13th Cavalry President Woodrow Wilson chose Major General John J. Pershing to lead a fruitless expedition into Mexico.
While the expedition didn't officially end until February 1917 the majority of U.S. troops were pulled out in January. Major General Pershing would later write the whole episode would "not be a very inspiring chapter for school children, or even grownups to contemplate. Having dashed into Mexico with the intention of eating the Mexicans raw, we turned back at the first repulse and are now sneaking home under cover, like a whipped curr with its tail between its legs."