By a successful coup d'etat, Victoriano Huerta (1854-1916) gained the presidency of Mexico on February 18, 1913, overthrowing Francisco I. Madero (1873-1913), but Huerta was opposed by the separate forces of Emiliano Zapata (1880-1919) in the south, of Venustiano Carranza (1859-1920) in the northeast, of Francisco "Pancho" Villa (1877-1923) in the north, and of Alvaro Obregon (1880-1928) in the northwest. These four opposing forces increased their military activities until they controlled about three-quarters of Mexico by the spring of 1914, confining Huerta and his followers to the areas around Mexico City, the capital, and Veracruz. US president Woodrow Wilson (1856-1924) refused to recognize Huerta's government, whose hostile acts resulted in American forces seizing and occupying Veracruz (April 21, 1914). When Villa's forces seized Zacatecas and Obregon's took Guadalajara and Queretaro, Huerta resigned as president. The rival leaders, Villa and Obregon, raced for the capital; Obregon arrived first and proclaimed his friend Carranza "First Chief" of Mexico. The leaders later met at Aguascalientes to organize a government in late 1914, but now Mexico was torn by anarchy; Villa and Zapata occupied Mexico City, while Carranza and Obregon took control of Veracruz. Although villa and Zapata had more troops and held about two-thirds of the country, Carranza was recognized by the United States and eight other nations in the Western Hemisphere as de facto president of Mexico. Carranza controlled the north-eastern border area with the United States, from which he could purchase arms; he also had the expert military assistance of Obregon and the shrewdness to promise the people social reform. In early 1915, Obregon and his troops occupied the capital, forcing Villa to flee to the surrounding countryside. Villa and his forces were pursued to the town of Celaya, where Obregon employed military tactics developed in World War I. His troops dug trenches and strung barbed wire around Celaya, and in a three-day battle in April 1915, they won a decisive victory over Villa, who treated northward. Villa's men pulled up railroad tracks to prevent pursuit by their foes. Both Villa and Zapata continued guerrilla warfare against Carranza, who later became president officially. Obregon was appointed minister of War.