1910 to 1919: The Border War along the U.S.-Mexico border saw U.S. forces occupy Veracruz for six months in 1914. U.S. troops intervened in northern Mexico during the Pancho Villa Expedition.[21] 1917 to 1920: The U.S. intervened in Europe during World War I. Over the next 18 months, the U.S. would suffer casualties of 116,708 killed and 204,002 wounded. U.S. troops also intervened in the Russian Civil War against the Red Army via the Siberian intervention and the Polar Bear Expedition's North Russia intervention.