Battle of Coconut Grove
Following the landing on Bougainville several actions were fought around the beachhead at Koromokina Lagoon and along the Piva Trail. As the beachhead was secured, a small reconnaissance party pushed forward and began identifying sites for airfield construction outside the perimeter.
To allow construction to begin, elements of the 21st Marine Regiment were ordered to clear the Numa Numa Trail. They were subsequently ambushed by a Japanese force and over the course two days a pitched battle was fought.
Elements of the 2nd Raider Battalion were brought up to reinforce the 21st Marines. Face with these veteran forces and being out numbered and outgunned the Japanese withdrew. By the end of the fighting, the Marines had gained control of a tactically important intersection of the Numa Numa and East–West Trails.