Battle of Olongapo The Battle of Olongapo was fought September 18 – 23 , 1899 , during the Philippine – American War . The battle featured both land and sea fighting of which the objective was the destruction of the single Filipino artillery gun in Olongapo , a menace to American ships crossing the nearby sea . Background . During the Spanish – American War that raged throughout 1898 , Olongapo was largely ignored by the American Asiatic Squadron , despite the fact that the Spanish had built a naval station there and the Americans had been warned about the presence of Spanish vessels in the area . The reason for this lay in the fact that when Commodore ( later Admiral ) George Dewey ' s fleet traversed the area on April 30 , 1898 , they failed to encounter any Spanish ships and , as a result , Dewey had continued on to Manila Bay where he destroyed the Spanish fleet under Admiral Patricio Montojo . After moving to Manila , the Americans focused on capturing the Spanish port in Cavite , which later became known as Sangley Point . After that , Filipino forces occupied the area and installed a gun battery at Kalaklan Point , from sea level , consisting of two artillery pieces : one six - inch and one three - inch . By 1899 , the Americans realized Olongapo ' s potential as a protecting harbor for vessels steaming between Manila and Hong Kong , so the Asiatic Squadron began patrolling the area during the summer . Battle . At first the Filipinos stationed in Olongapo decided not to fire at the American patrol . However , on September 18 , 1899 , after noticing the routine patrolling by the squadron , the Filipinos fired at the armed transport " Zafiro " . Undamaged , " Zafiro " withdrew and reported the incident . From Sangley Point , the Americans dispatched the protected cruiser " Charleston " , which fired at Filipino - held Olongapo with her eight - inch guns , silencing the single enemy battery . She then began to withdraw back to Sangley Point . As the cruiser moved away , the Filipino battery fired a single parting shot , provoking the Americans . On September 23 , the Americans returned to Olongapo with a stronger force , bringing the monitor " Baltimore " and the gunboat " Concord " in addition to " Zafiro " and " Charleston " . " Baltimore " opened fire with her ten - and twelve - inch guns . Due to the heavy American bombardment , the Filipino battery was only able to respond with a single shot . After the bombardment was lifted , " Charleston " landed 180 sailors and 70 marines . As the landing party began their advance , the ships stopped firing but they were met by Filipinos from the naval yard . A short battle ensued in the main part of Olongapo , during which one American was wounded . The Americans then raced to the single battery at Kalaklan Point , and destroyed it completely with three charges of guncotton . As soon as they achieved their mission , the Americans withdrew to their ships . Olongapo remained under the Filipinos , but the battery – badly damaged in the explosion – no longer posed a threat to American intentions in the area . Aftermath . With the single Filipino battery gone , trade vessels as well as American patrols were able to freely use the trade route past Olongapo . Emilio Aguinaldo effectively disbanded the regular Filipino army due to continuing American advances by November 13 , 1899 , which divided the force into bands of guerrillas . On December 10 , 1899 , an American force of 90 soldiers under Major Robert Spence captured Olongapo . Their force was augmented by the ships " Baltimore " and " Oregon " , commanded by Rear Admiral John Watson .