After that, Filipino forces occupied the Olongapo area and installed a gun battery at Kalaklan Point, 1,000 feet (300 m) from sea level, consisting of two artillery pieces: one six-inch and one three-inch.

[1] 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.

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.

[1] 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.

[1] 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.