Amid growing resentment over the authoritarian regime of General Porfirio Díaz, revolution broke out in Mexico following the 1910 presidential election. Opposition leader Francisco I. Madero fled to San Antonio and issued a call to arms on November 20, 1910. Texas and the borderlands continued to play a significant role throughout the decade-long conflict. Political exiles and refugees MIGRATED to the state en masse, integrating with existing Mexican-American communities and organizing chapters of the Partido Liberal Mexicano. All did not find safety on the other side of the border, however. Tejanos living in the borderlands already faced considerable DISCRIMINATION, between general political disenfranchisement and the recent transfer of hundreds of thousands of acres of historically Mexican land to white settlers. Proximity to the revolution led to further racial conflict, with federal and state officials fearing that the violence might incite oppressed minorities to similarly take up arms against the United States. The release of the Plan of San Diego—a manifesto calling upon various ethnic groups to liberate the states of Texas, New Mexico, Arizona, California, and Colorado from American control—in 1915, coupled with border raids of ranches and railroad lines, led to widespread panic among Anglos living in border counties. Consequently, the region entered a period of state-sanctioned racial terror known as La Matanza, with TEXAS RANGERS and civilian vigilantes killing thousands of Mexican immigrants and Tejanos and forcing countless more across the border until the Mexican Revolution ended in 1920.