The 'Battle of Davao' was one of the first undertakings in the Japanese invasion of the Philippine islands group and designed to provide the Japanese forces with Davao, together with the island of Jolo in the Sulu islands group (19/25 December 1941).
The Japanese primary purpose was to cut off the possibility of reinforcements reaching Luzon island from the south, and to complete the encirclement of US and Filipino forces there, while the secondary purpose was the establishment of a base from which Lieutenant General Hitoshi Imamura’s 16th Army could launch an invasion of British North Borneo and the Netherlands East Indies.
Davao was the economic centre of southern Mindanao, and before the start of the war was the hub of Japanese settlement and economic activity in the Philippine islands group. For the invasion of Davao, Major General Shizuo Sakaguchi’s 56th Division organised two detachments totalling 5,000 men. The 'Miura' Detachment, under the command of Lieutenant Colonel Toshio Miura, comprised the 1/33rd Regiment and the 'Sakaguchi' Detachment, under Sakaguchi’s command, comprised the 146th Regiment as well as single tank and artillery battalions. Whereas Lieutenant General Masaharu Homma’s 14th Army was responsible for the invasion of the Luzon, Sakaguchi’s forces was part of Imamura’s 16th Army and was scheduled to continue the Japanese advance south to Tarakan in the Netherlands East Indies after Davao had been secured. For the Jolo portion of the mission, Sakaguchi was to be assisted by the the 1st Kure Special Naval Landing Force, which had just completed its task of securing Legazpi on Luzon.
The area of Davao was in theory defended by 2,000 men of the Philippine army’s 101st Regiment under the command of Lieutenant Colonel Roger B. Hilsman. As with other units in the Philippine army, this force was only partially trained, and suffered from a serious shortage of equipment.
Davao was of concern to the Imperial Japanese navy as it had an US naval base and was only 500 miles (805 km) from the major Japanese military centre in the western Pacific, Palau. However, at the start of the war, only the seaplane tender William B. Preston, with three operational Consolidated PBY flying boats, was in the harbour. Unaware of this, on 8 December the Japanese launched an attack on Davao, using 13 dive-bombers and nine fighters launched from the light aircraft carrier Ryujo, with the destroyers Hayashio, Kuroshio, Oyashio and Natsushio making a high-speed run for the entrance of Davao harbour to catch any escaping vessels. The raid was somewhat of a wet squib, as the Japanese pilots did not even recognize William B. Preston as a warship and managed only to destroy two of her PBY 'boats as the third was currently absent on a mission.
The Davao Attack Force was commanded by Rear Admiral Raizo Tanaka departed Palau on 17 December with the troops in five transport vessels escorted by the light cruiser Jintsu and the destroyers Amatsukaze, Hatsukaze, Kuroshio, Oyashio, Hayashio and Natsushio, together with the carrier Ryujo and the seaplane carrier Chitose. Distant cover was provided by the heavy cruisers Nachi, Haguro and Myoko. On the afternoon of 19 December, Ryujo launched aircraft to destroy the radio station at Cape San Augustin, and the Chitose launched reconnaissance aircraft, which flew over Davao.
The Japanese transport vessels arrived at Davao toward 00.00, and the landing started at 04.00, with the 'Miura' Detachment coming ashore to the north of the city and the 'Sakaguchi' Detachment to its south-west. The only opposition was a single machine gun squad, which fired on the 'Miura' Detachment before it was destroyed by a direct hit by a shell from a Japanese destroyer. However, since the 'Miura' Detachment had suffered casualties, Sakaguchi was forced to commit reserve forces he had been reserving for the Jolo portion of the operation. By 10.30, Hilsmen had pulled his men out of the city and moved to the north-west into the hills. By 15.00, the city and airfield were in Japanese hands, and by evening a seaplane base was established to the south of the urban area. On 20 December, as Sakaguchi was reorganising his forces into nine transport vessels for the landing on Jolo island, he was attacked by a force of nine Boeing B-17 Flying Fortress four-engined heavy bombers operating from Darwin in northern Australia. Visibility was poor, and the bombers caused little damage, although the Kuroshio suffered four men wounded.
The Jolo Attack Force departed Davao of 23 December and reached its destination in the afternoon 24 December. Jolo, the capital of the former Sultanate of Sulu, was defended only by 300 members of the Philippine Constabulary. The Japanese landed on the morning of 25 December and encountered no resistance.
The advance landings by the Japanese in southern Mindanao and Jolo island had little to no impact on the overall campaign in the Philippine islands group, but placed the Japanese in an excellent position for their planned 'B' (ii) invasion of Borneo and then the Netherlands East Indies early in 1942.