Germany had long sought to incite a war between Mexico and the United States, which would have tied down American forces and slowed the export of American arms to the Allies. The Germans had aided in arming Mexico, as shown by the 1914 Ypiranga Incident. German Naval Intelligence officer Franz von Rintelen had attempted to incite a war between Mexico and the United States in 1915, giving Victoriano Huerta $12 million for that purpose. The German saboteur Lothar Witzke, responsible for the March 1917 munitions explosion at the Mare Island Naval Shipyard in the San Francisco Bay Area, and possibly responsible for the July 1916 Black Tom explosion in New Jersey, was based in Mexico City. The failure of United States troops to capture Pancho Villa in 1916 and the movement of President Carranza in favor of Germany emboldened the Germans to send the Zimmermann note.