Although diplomatic rumblings continued between Mexico and the United States after the beginning of the American incursion, the Carranza administration grudgingly accepted the facts on the ground and did not risk an open confrontation with the U.S. forces. This development caught the German government by surprise. All indications had been that Carranza would resist the Punitive Expedition. Through Arnold Krumm-Heller, Minister von Eckardt’s agent next to Carranza, and the diplomat’s own understanding of the disposition of the Mexican government towards the U.S., Carranza was supposed to militarily oppose the American forces. The immediate reaction of Carranza threatening war in case of U.S. forces crossing the border allows the supposition that, at least, the First Chief had contemplated resistance. However, promises of German arms and ammunition support were no match for the prospect of fighting the United States army along a border of twelve hundred miles.
Rumors of impending hostilities between the United States and Mexico ran rampant in Washington, which Ambassador Count Bernstorff dutifully related to his superiors in Berlin. Despite the pressure from political opponents to mount a full military intervention, cabinet members, and Wall Street, even the customs agent, Zach Lamar Cobb, the Wilson administration had no interest in risking a quagmire of all Mexican factions uniting against a common enemy. To Wilson’s relief, Carranza blinked first, mainly because he had decided on an alternate tactic to open confrontation. The First Chief knew when brinkmanship had to give way to acquiescence after the earlier Plan de San Diego raids in the summer and fall of 1915. He backed down from direct confrontation, but carefully monitored the progress of the American forces, limiting the supply lines by forbidding the use of Mexican railways. Carranza caged the Americans into a narrow north-south corridor between the Casas Grandes and Santa Maria rivers of Chihuahua while hunting down Villa with his own forces. Simultaneously, he re-activated the Plan de San Diego to pressure the American forces to leave.
The German government in Berlin anxiously followed the situation in Mexico. The German ambassador in Washington, Count Bernstorff, accurately reported on the reciprocal agreement for hot pursuit that Carranza and Wilson had tentatively concluded, but added his impression that Wilson welcomed the Columbus attack for political reasons. “If some anti-German newspapers are claiming, we [the German government] had bribed Villa [to conduct the attack], one could with the same justification claim that the [American] president had bribed him [Villa].” The German ambassador reported at the end of March that the public sentiment, as well as “the most influential circles” of the country expected a full-scale intervention. Count Bernstorff noted, “If the president is able to continue to operate the same way, the country will slowly but surely slide into intervention without any domestic resistance. That,” continued Count Bernstorff, “would in my own, humble opinion, secure the re-election of Mr. Wilson.”
Despite the ambassador’s factual reporting, his cynical opinion of President Wilson’s motivation confirmed the hope of most German government officials that a war between Mexico and the United States was becoming inevitable. Count Bernstorff added in his next report that rumors of Carranza troops defecting and joining Villa were false but that “Mexicans are observing the American incursion with quite some suspicion.” The ambassador added an important fact: “Almost the entire regular army of the United States is now in Mexico or congregating along the border.” Count Montgelas commented on Bernstorff’s statement that accusations of Germany’s involvement in the Columbus attack were “ridiculous” with the penciled remark “regrettably [i. e. “I wished we would have been behind the attack.”].”