1918 – Mexican Revolution: Battle of Ambos Nogales: U.S. Army forces skirmish against Mexican Carrancistas and their German advisors in the only battle of World War I fought on American soil
. The Battle of Ambos Nogales was an engagement fought on 27 August 1918 between Mexican forces and elements of US Army troops of the 35th Infantry Regiment, who were reinforced by the Buffalo Soldiers of the 10th Cavalry Regiment, and commanded by Lt. Col. Frederick J. Herman. The American soldiers and militia forces were stationed in Nogales, Arizona, and the Mexican soldiers and armed Mexican militia were in Nogales, Sonora. This battle was notable for being a significant confrontation between US and Mexican forces during the Border War which took place in the context of the Mexican Revolution and the First World War. This occurred after the Zimmermann telegram during World War I, when the international border between the two Nogaleses was a wide-open boulevard named International Street. Several previous fatal incidents had occurred in this area, which helped increase international tensions and led to armed conflict. This included the claim of German military advisors as agitators with Mexican Villa rebels, claims of racism and border politics. As a result of this battle, the US and Mexico agreed to divide the two border communities with a chain-link border fence, the first of many permanent incarnations of the U.S.–Mexico border wall between the two countries.