Many city leaders opened their cities to his informal army, and several "mantuanos" (among them the "Marqués" of Casa Leon) became his collaborators. This movement was reinforced by the earthquake on 26 March 1812 and the loss on 30 June of Puerto Cabello under the then-Colonel Simón Bolívar to royalist prisoners who managed to take over San Felipe Fort. Monteverde's vanguard under Francisco Marmól entered Barquisimeto on 2 April after the city defected to the royalist side on 31 March. Eventually he had an army large enough to march on Valencia, the site of a royalist uprising the previous year. After winning a battle against republican troops defending the city on 3 May, he was welcomed by the city. His next goal was Caracas. In June, Monteverde arrived in the proximity of La Victoria and San Mateo, forcing Generalissimo Francisco de Miranda to retreat. Monteverde's advance culminated in a capitulation agreed between Miranda and Monteverde on 25 July 1812 after the Battle of San Mateo. (Miranda never signed the final version, but it had been approved by his representatives in the negotiations.)