its other major objective of capturing Villa. However, between the date of the American withdrawal and Villa's retirement in 1920, Villa's troops did not again successfully raid the United States. National Guard call-ups Between June 1915 and June 1916 raiders from Mexican irregulars carried out 38 raids on U.S., resulting in the deaths of 26 soldiers and 11 civilians. Following the attack on Glenn Springs, the Army transferred three regiments of active duty soldiers to the border area. On May 8, state militia units from Texas, Arizona, and New Mexico were activated. On June 15, 1916, another attempted raid by Mexican border-crossers, this at San Ygnacio, Texas, 30 miles downstream from Laredo, was repulsed by soldiers with casualties to both sides. As a result, using powers granted by passage of the National Defense Act of 1916, Wilson on June 18 fully mobilized Guard units from the remainder of the states and the District of Columbia for duty on the border. More than 140,000 National Guard troops were called up, but only two regiments, the 1st New Mexico Infantry and the 2nd Massachusetts Infantry, were actually assigned to the Mexican Expedition, and those to guard the base at Columbus. Historian Clarence C. Clendenen asserts that although no Guard units officially crossed into Mexico at any time, soldiers from the two regiments at Columbus did enter Mexico to perform various tasks. Wide differences in proficiency existed between various guard units in training, leadership and equipment, so that for the most part units came to the border with only basic drilling as experience. Units were initially assigned as static guards for railroad bridges and border crossing points, but as training made them more proficient, they were assigned an increasing responsibility for the patrolling the border that resulted in encounters with smugglers and bandits who still posed an occasional threat. Records of the Utah National Guard indicate that it participated in three skirmishes after it arrived at Camp Stephen J. Little on the Arizona border in July 1916. The final action of the three, occurring January 26, 1917, resulted in an all-day border skirmish between Utah cavalrymen and Mexicans in which the guardsmen were reinforced and ten Mexicans were killed or wounded. While incapable of conducting organized combat operations with other units, the border security mission proved a training environment for the officers and men of the National Guard, who were again inducted into