While attached to the USS Pampanga, Harrison was one of a shore party moving in to capture Mundang, on the island of Basilan, Philippine Islands, on 24 September 1911. Harrison instantly responded to the calls for help when the advance scout party investigating a group of nipa huts close to the trail, was suddenly taken under point-blank fire and rushed by approximately 20 enemy Moros attacking from inside the huts and from other concealed positions. Armed with a double-barreled shotgun, he concentrated his blasting fire on the outlaws, destroying 3 of the Moros and assisting in the rout of the remainder. By his aggressive charging of the enemy under heavy fire and in the face of great odds, Harrison contributed materially to the success of the engagement.