 Leaving his cruisers at Kavieng , Mikawa gathered all 21 of his destroyers at the Japanese naval base in the Shortlands on 31 January to begin the evacuation runs . Rear Admiral Shintaro Hashimoto was placed in charge of this group of destroyers , titled the Reinforcement Unit . The " R " Area Air Force 's 60 floatplanes were tasked with scouting for the Reinforcement Unit and helping defend against Allied PT boat attacks during the nighttime evacuation runs . Allied B @-@ 17 bombers attacked the Shortlands anchorage on the morning of 1 February , causing no damage and losing four aircraft to Japanese fighters . This same day , the IJA 's 6th Air Division raided Henderson Field with 23 " Oscar " s and six " Lily " s but caused no damage and suffered the loss of one fighter . 
