Soon, 6,000 Dominican insurgents rallied to Gaspar Polanco's army, which besieged Fort San Luis and its 800-man Spanish garrison and captured it on September 13. A steam frigate went to the support of Spanish troops holed up in the fort at Puerto Plata and drove off the rebels by firing grapeshot. Self-appointed president Jose Antonio Salcedo unsuccessfully lobbied for United States aid in the war, but the guerrillas killed a total of 1,000 Spaniards by March 1864, while another 9,000 had perished from fever.