The 'Battle of Mindanao' resulted in the Japanese seizure of Mindanao, the second largest element of the Philippine islands group, from US and Filipino forces (16 December 1941/10 May 1942).
The island of Mindanao, the most southerly of the Philippine island group’s large islands, was not as well developed as Luzon, the largest island. Mindanao is irregularly shaped, about 300 miles (485 km) across, with a coast indented by numerous inlets, bays and gulfs. The island covers 36,906 sq miles (95586 km˛). In 1942, the island possessed only a poor road system, although there were two highways. Route 1 ran from Digos on Davao Gulf on the central part of the south-eastern coast to the north-east across the island to Parang on the western coast, cut across the base of the Zamboanga peninsula, and followed the northern coast to the extreme north-eastern end. Route 3 extended in winding fashion from Cagayan on the central part of the northern coast to the south to link with Route 1 half-way between Parang and Digos. While villages and towns lined the northern and eastern coasts, there were few on the other coasts other than the area around Davao Gulf, where Davao city is located as the island’s principal town. The three important Del Monte airfields were located at Tankulan, 10 miles (16 km) inland from the central part of the northern coast. The heavy bombers of Major General Lewis H. Brereton’s US Far East Air Force had been moved there from Luzon to protect them from air attack yet still able to attack Japanese shipping approaching the Philippine islands group from the north. The island is mountainous with the Diuata mountains running along the eastern coast, but the island’s highest peak is Mt Apo, a 9,691-ft (2954-m) volcano on the western side of Davao Gulf. The Agusan river flows to the north along almost the entire length of the eastern coast along the inland side of the Diuata mountains through a marshy valley before debouching into the Mindanao Sea. The shorter Mindanao river, also running through a swampy valley, is located on the central part of the western part of the island to empty into Bongo Bay. Both of these rivers are navigable. The Zamboanga peninsula juts almost 150 miles (240 km) to the west from the upper part of the western coast and then turns to the south-west.
On 16 December 1941, the 'Sakaguchi' Detachment from the Palau islands group with the headquarters of the 56th Mixed Infantry Group under the command of Major General Shisuo Sakaguchi with the 148th Regiment and Special Naval Landing Force elements, landed at Davao. This force was detached from the 16th Army otherwise involved in the occupation of Borneo and Java. Landing with it was the 'Miura' Detachment with the 1/33rd Regiment of the 16th Division.
Davao was defended by some 2,000 Filipino troops, which were soon forced to withdraw, and the 'Matsumoto' Detachment departed this port on 23 December to occupy the island of Jolo to the west, which provided a vital link in the maritime line of communication between the Philippine islands group to the north-east and Borneo and the Netherlands East Indies to the south-west. The 'Miura' Detachment remained to establish a seaplane base, and the airfield outside Davao was also put into service. Jolo was occupied on 24 December after the 'Miura' Detachment had defeated a 300-man force of the Philippine Constabulary. Both Davao and Jolo were then used as launch sites for operations in Borneo to the south-west. The Japanese made no effort to secure the entire island of Mindanao during the first months of 1942. The 'Miura' Detachment was contained at Davao and Digos, and the Philippine army units, assigned defence sectors about the island, continued to train. General Douglas MacArthur, the commander-inc-chief of the US Armed Forces in the Far East, hoped that Mindanao would be able to hold out until he was able to mount an offensive from Australia and then make use of the island as a forward base of operations in the planned reconquest of the rest of the Philippine islands group.
On 29 April, after securing Cebu, the 'Kawaguchi' Detachment, based on the 124th Regiment, landed in the Moro Gulf on the central part of the western side of Mindanao and advanced north up Route 1 as well as to the east, while the 'Miura' Detachment moved to the west on Route 1 from Digos to meet it. About 220 men of the 32nd Naval Base Force landed at Zamboanga on the northern coast of the Zamboanga peninsula on 2 March and established a seaplane base. After taking Panay, the 'Kawamura' Detachment, based on the 41st Regiment, landed at Cagayan in Macajalar Bay near the point at which Route 1 and Route 3 joined on the central pt of the northern coast. While the Filipino troops resisted to the extent of their capabilities, on 10 May the Mindanao Force surrendered.
Lieutenant General Jonathan Wainwright, the commander-in-chief of the US Forces in the Philippines, released Major General William F. Sharp, commanding the Visayan-Mindanao Force, to the command of MacArthur when Wainwright surrendered Corregidor, but on the night of 7 May he attempted to reassume command so as to be able to order the force to surrender as he feared that the 11,000 troops who had surrendered on the the fortified islands of Manila Bay might be massacred if the southern forces did not meet Japanese demands. MacArthur ordered Sharp to ignore Wainwright. A truce was arranged and meetings held between Sharp and the Japanese. Once appraised of the situation in the north by a staff officer sent by Wainwright, Sharp surrendered his forces on 10 May. Many of the far-flung units were without communications and some were already executing raids and harassing attacks on the Japanese. The island of Panay surrendered on 20 May, and the islands of Leyte and Sumay on 26 May, but in each only about 10% of the officers and men surrendered, most of the other 90% moving into the hills to continue the war as guerrillas. The 'Nagano' Detachment, based on the 62nd Regiment, occupied the islands of Negros, Bohol, Leyte and Samar between 20 and 25 May. Negros did not surrender until 3 June and then only about 40% of the troops accepted captivity rather than disappearing to fighter as guerrillas. By 9 June, the units that had decided to surrender had done so. At one time or another, about 7,000 US civilians were held in an erratic internment, with some not confined until 1943 and others released later. Many of the elderly and infirm were never interned. Most were detained in camps on Luzon island, where in general they were not overly mistreated. US prisoners of war were confined in camps under harsh conditions throughout the Philippine islands group, although most were on Luzon. Many of the prisoner of war were shipped to Burma, Japan and China under extremely brutal conditions as forced labourers.
A total of 129,400 men of the Imperial Japanese army, 12,800 men of the Imperial Japanese army air force and 49,800 men of the Imperial Japanese navy, including the 3rd Fleet, had been committed to the conquest of the Philippine islands group. Lieutenant Generwal Masaharu Homma’s (from 1 August 1942 Lieutenant General Shizuichi Tanaka’s) 14th Army was detached from General Count Hisaichi Terauchi’s Southern Expeditionary Army Group on 29 June and placed under the direct control of the Imperial General Headquarters. It was ordered to stabilise and secure the Philippine islands group, and to establish a military government. After his replacement by Tanaka, Homma was recalled to Japan and accorded a conquering general’s welcome, but was not permitted to deliver his report to the Emperor Hirohito as he was considered disgraced for his refusal to continue the attack on the Bataan peninsula without reinforcement and for his failure to meet the exacting Japanese schedule. Homma was accordingly placed on the reserve list in August 1943 and, after the war he was tried for war crimes, condemned and executed by firing squad in the Philippines on 3 April 1946; several of his subordinates were hanged.