In the late summer of 1914 war in Europe was far from the minds of Americans. To be sure, there were plenty of Americans of European descent, and many not far removed from the “old country.” The turn of the century had brought a flood of immigration from Europe. In Colorado, where many of the new immigrants worked in the mines or in the steel mills, they were typically from Italy, Ireland, or the countries of Austria-Hungary, especially Slovenia. They would have had concerns about their families fighting against Serbia or Russia at the time.

But if America thought much about war, we already had one right next door, where a revolution in Mexico had overthrown the dictator Porfirio Diaz in 1911. The newly-elected president, Francisco Madero, was murdered after a military coup in early 1913. Because of the unstable situation, U.S. president Taft sent a large military force to Texas and stationed them along the Rio Grande to protect Americans in the region. This show of American military force caused Mexican militants to redirect their violence from their own countrymen to Americans. Woodrow Wilson took office as president the following month, but refused to recognize the legitimacy of the new government led by Victoriano Huerta, and eventually supported the rebels trying to overthrow him. As a result of the U.S. position, violence toward Americans intensified and there were incidents of murder, robbery, kidnapping for ransom and property destruction.

Pancho Villa took out his anger by attacking the town of Columbus, New Mexico with 500 of his men in March 1916, resulting in 24 American casualties. The tense situation with Mexico resulted in the establishment of the 3rd Reserve Engineer’s Regiment, precursor to the 13th Engineers.

In response to the violence, President Wilson sent 4,800 regular army troops under General John “Blackjack” Pershing to defend the border towns and their citizens. U.S. troops landed in Veracruz in April 1914, the Huerta government fell apart by July, and U.S. troops were withdrawn in November. But the rebel leaders opposed to Huerta couldn’t agree among themselves, and continued fighting all year long. When the faction led by Venustiano Carranza came out on top by the end of 1915, the U.S. recognized his government. This infuriated his major opponent, a bandit-turned-revolutionary named Francisco “Pancho” Villa, and he took out his anger by attacking the town of Columbus, New Mexico with 500 of his men in March 1916, resulting in 24 American casualties. A firm response was required, and immediate steps were taken to organize a punitive expedition; within a week Pershing and his troops set off into Mexico to find Pancho Villa and disperse his men.

The incursion by the U.S. troops was denounced by the Mexican government, and while Pancho Villa and his men were never found, the expedition engaged in a battle with the regular Mexican army on 21 June 1916 at Carrizal, Chihuahua, which resulted in nearly 50 American casualties.

War would probably have been declared but for the critical situation in Europe. Even so, virtually the entire regular army was eventually involved, and most of the National Guard had been federalized and concentrated on the border before the end of the affair.

The Mexican situation resulted in the establishment of the 3rd Reserve Engineer’s Regiment. As Pershing was preparing his punitive expedition, the question of railway operations in Mexico became a serious one. Not only would supplies need to follow the invading troops, but it was assumed that the Mexicans would try to destroy the railroads as they headed south, making reconstruction efforts necessary. Samuel Felton, president of the Chicago Great Western Railway, was called upon to help organize the railroad efforts, and was later appointed director general of military railways. The railroads quickly agreed to supply locomotives, cars, rail and track material for the Mexican campaign. Because the Mexican and American governments worked to reach a negotiated settlement, the materiel accumulated by the railway unit was not used in Mexico, and was eventually sent to Europe for the war effort there.