In a period in February 1913, known as the Ten Tragic Days, Madero and his vice president Pino Suárez were forced to resign and then assassinated. The counter-revolutionary regime of General Victoriano Huerta came to power, backed by the United States and its ambassador Henry Lane Wilson, business interests, and supporters of the old order. Huerta remained in power until July 1914, when he was forced out by a coalition of different regional revolutionary forces, including the forces of Pancho Villa and Emiliano Zapata. Wealthy landowner Venustiano Carranza formed the "Constitutionalist" political faction, and with military forces under the leadership of Álvaro Obregón, played an important part in defeating Huerta. When the revolutionaries' attempt to reach political agreement failed, Mexico plunged into a civil war (1914–15). Carranza emerged as the victor in 1915, defeating the Villistas and forcing Zapata back to guerrilla warfare. Zapata was assassinated in 1919 by agents of President Carranza. Many scholars consider the promulgation of the Mexican Constitution of 1917 as the end point of the armed conflict.