The roots of the Mexican republic can be traced to two documents drafted during the early independence struggle against Spain: Los sentimientos de la nación (1813), by José María Morelos y Pavón, and the Constitution of Apatzingán (1814). These documents introduced the ideal of a republic based on liberal political institutions and respect for individual rights. Mexico's independence was attained, however, by an alliance of liberal and ultraconservative forces under the leadership of Agustín de Iturbide.