The Constitutional Army (Spanish: Ejército constitucionalista; also known as the Constitutionalist Army) was the army that fought against the Federal Army, and later, against the Villistas and Zapatistas during the Mexican Revolution. It was formed in March 1913 by Venustiano Carranza, so-called "First-Chief" of the army, as a response to the murder of President Francisco I. Madero and Vice President José María Pino Suárez by Victoriano Huerta during La Decena Trágica (Ten Tragic Days) of 1913, and the resulting usurpation of presidential power by Huerta.