The Actions along the Matanikau—sometimes referred to as the Second and Third Battles of the Matanikau—were two separate but related Cause_to_be_included engagements Hostile_encounter , which took place Process_start in the months of September and October 1942 , among a series of engagements between the United States and Imperial Japanese naval and ground forces Causation around the Matanikau River on Guadalcanal ( island in the southwestern Pacific , northeast of Australia ) during the Guadalcanal Campaign .