The poorly equipped Filipino troops were easily overpowered by American troops in open combat, but they were formidable opponents in guerrilla warfare. Malolos, the revolutionary capital, was captured on March 31, 1899. Aguinaldo and his government escaped, however, establishing a new capital at San Isidro, Nueva Ecija. On June 5, 1899, Antonio Luna, Aguinaldo's most capable military commander, was killed by Aguinaldo's guards in an apparent assassination while visiting Cabanatuan, Nueva Ecija to meet with Aguinaldo. With his best commander dead and his troops suffering continued defeats as American forces pushed into northern Luzon, Aguinaldo dissolved the regular army on November 13 and ordered the establishment of decentralized guerrilla commands in each of several military zones. Another key general, Gregorio del Pilar, was killed on December 2, 1899 in the Battle of Tirad Pass—a rear guard action to delay the Americans while Aguinaldo made good his escape through the mountains.