The action also was the first time the U.S. Army used plunging fire by machine guns to support an attack. The columns pushed deeper into Mexico, increasing tensions between the United States and the Carranza government. On April 12, 1916, Major Frank Tompkins and Troops K and M, 13th Cavalry, numbering 128 men, were attacked by an estimated 500 Mexican troops as they were leaving the town of Parral, 513 miles into Mexico and almost to the state of Durango, following violent protests by the civilian populace. Tompkins had been personally ordered to avoid a straight-up engagement with de facto government troops to prevent war between the countries and so used a rear guard to keep the Carrancistas at a distance during a retreat to his starting point, the fortified village of Santa Cruz de Villegas. Two Americans were killed in the skirmishing, one was missing from the rear guard, and another six were wounded, while the Carrancistas lost between fourteen and seventy men, according to conflicting accounts. The battle marked a turning point in the campaign. Military opposition by Carranza forced a halt in further pursuit while diplomatic conversations took place by both nations to avoid war. Only four days earlier, on April 8, Army Chief of Staff General Hugh L. Scott had expressed to Secretary of War Baker that Pershing had virtually accomplished his mission and that it was "not dignified for the United States to be hunting one man in a foreign country". Baker concurred and so advised Wilson, but following the fight at Parral the administration refused to withdraw the expedition, not wanting to be seen as caving in to Mexican pressure during an election year. Instead, on April 21 Pershing ordered the four columns that had converged near Parral to withdraw to San Antonio de Los Arenales. A week later he assigned the cavalry regiments, including the newly arrived 5th Cavalry, to five districts created in central Chihuahua in which to patrol and seek out the smaller bands. While executing the withdrawal order, Dodd and a portion of the 7th Cavalry fought an engagement on April 22 with about 200 Villistas under Candelaro Cervantes at the small village of Tomochic. As the Americans entered the village, the Mexicans opened fire from the surrounding hills. Dodd first sent patrols out to engage the Villistas' rear guard, to the east of Tomochic, and after these were "scattered",