Carranza maintained a policy of formal neutrality during the war, influenced by the anti-American sentiment that the United States' various interventions and invasions during the last century had caused. Victoriano Huerta had conspired with the U.S. ambassador Henry Lane Wilson in February 1913, to oust the democratically elected President Francisco I. Madero and Vice President José María Pino Suárez, in a "coup d'état" during a period known as "La decena trágica". President Woodrow Wilson also ordered the invasion of Veracruz in 1914, resulting in the death of 170 Mexican soldiers and an unknown number of civilians. The assassination of Madero and José María Pino Suárez triggered a civil war that ended when the Constitutional Army defeated the forces of former ally Pancho Villa in the Battle of Celaya in April 1915. The partial peace allowed a new liberal constitution to be drafted in 1916 and proclaimed on February 5, 1917.