effect this was an intervention in Mexican politics, and to Mexicans it meant the United States had condemned Díaz." After Díaz was forced to resign in 1911 and Francisco I. Madero was elected president in October 1911, U.S. president Taft was a lame duck, having lost the presidential election of 1912. He would remain in office until the March 1913 inauguration of Woodrow Wilson and during that interval, Taft's Ambassador to Mexico, Henry Lane Wilson actively sought to oust democratically elected Mexican president Madero. Lane Wilson was initially sympathetic to the Madero regime, but quickly came into conflict with it and conspired with General Victoriano Huerta to oust Madero. The anti-Madero coup took place in February 1913, known as the Ten Tragic Days, which saw the forced resignations of Madero and his vice president, followed immediately by their murders. The United States government under newly inaugurated president Woodrow Wilson refused to recognize Huerta's government. Under President Wilson, the United States sent troops to occupy Veracruz, with the dispute defused through a peace conference in Canada. Anti-Huerta forces in the north under Venustiano Carranza and in the south under Emiliano Zapata forced the resignation of Huerta in July 1914. A civil war between Carranza and Zapata broke out in 1915, with the U.S. recognizing Carranza's Constitutionalist faction. The US supplied arms to Carranza's army. Pancho Villa was at first supported by Washington, but he was defeated and lost most of his support. He was angered by the U.S. switch to recognition of his rival. To draw the US into Mexico he attacked the border village of Columbus, New Mexico, killing US citizens in 1916. The U.S. Army under Gen. John J. Pershing pursued him in a punitive mission, known as the Pancho Villa Expedition, but failed to capture him. Carranza demanded the U.S. to withdraw across the border. Diplomatic relations in the Díaz era Díaz opened Mexico to foreign investment of Britain, France, Germany, and most especially the United States. Mexico–United States relations during Díaz's presidency were generally strong, although he began to strengthen ties with Great Britain, Germany, and France to offset U.S. power and influence. Mexico was extremely important to U.S. business interests and Taft saw Díaz as key to protecting those investments. Taft met Díaz in person on the U.S.-Mexico border in 1909, an historic event in itself since it was the first trip of a sitting U.S.