The 'Battle of Ormoc Bay' was a series of air/sea battles between Japanese and US forces in the Camotes Sea of the Philippine islands group (11 November/21 December 1944).

The battles resulted from Japanese operations to reinforce and resupply their forces on Leyte islands and US attempts to interdict them within 'King II'.

After securing naval control over the Western Pacific by the middle of 1944, US forces attacked the Philippine islands group with the 'King II' landing at Leyte Gulf on the eastern side of Leyte island on 20 October. The island of Leyte was defended by about 20,000 Japanese troops, and General Douglas MacArthur thought that the occupation of Leyte would be only the prelude to the major engagement on Luzon island. For the Japanese, the maintenance of their position in the Philippine islands group was essential as the loss of these islands would make it possible for the Allies to sever the flow of Japan’s strategically vital oil supplies from Borneo and Sumatra.

The Imperial Japanese navy responded to the 'King II' landings with the Combined Fleet's 'Sho 1' attack that led to the 'Battle of Leyte Gulf' on 23/26 October. In this massive naval engagement, the Japanese navy was effectively destroyed as a strategic force. However, this was not at first clear, and the Japanese commander-in-chief in the Philippines and of the 14^th Area Army, General Tomoyuki Yamashita, believed that the US Navy had suffered severe losses and that the Allied land forces might therefore be vulnerable. Accordingly, he began to reinforce and resupply the garrisons on Leyte, and over the course of the battle the Japanese sent nine convoys to the island, landing around 34,000 troops from the 1^st Division, 8^th Division, 26^th Division, 30^th Division and 102^nd Division. Ormoc City at the head of Ormoc Bay on the western side of Leyte was the main port on the island and the primary destination of the reinforcement convoys.

Decryption of Japanese signal traffic sent using the 'Purple' cipher alerted the Allies to the concentration of Japanese shipping around Leyte, but this was initially interpreted as the shipping for an evacuation. By the first week of November, however, the situation had become clear and the Allies started to interdict the convoys.

On 8/9 November, the Japanese despatched two convoys from Manila to Ormoc Bay. The convoys were spaced one day apart so that the destroyers escorting the first convoy could double back and escort the second. However, the convoys were detected on 9 November and attacked by land-based aircraft of Major General Ennis C. Whitehead’s 5^th Air Force. On 10 November the 38^th Bomb Group, based on Morotai island, sent 32 North American B-25 Mitchell twin-engined medium bombers escorted by 37 Republic P-47 Thunderbolt fighters to attack the 'TA-4' convoy near Ponson island. Arriving over the convoy just before 12.00, the bombers attacked in pairs at minimum altitude, sinking the two largest transports, the 11,910-ton Takatsu Maru and 6,825-tonKashii Maru, disabling a third ship and sinking two of the patrol craft escorts in exchange for seven bombers. The Japanese transports had been able to land the 10,000 soldiers they had been carrying, although with only a fraction of the supplies.

On 11 November, Admiral William F. Halsey, commander of the US 3^rd Fleet, ordered an attack by 350 aircraft of Task Force 38 on the combined convoys. Four destroyers (Shimakaze, Wakatsuki, Hamanami and Naganami) and four transports (3,143-ton Mikasa Maru, Taizan Maru, 4,639-ton Seiho Maru and 4,982-ton Tensho Maru) were sunk, and many of the 4,000 soldiers on board were killed. Rear Admiral Mikio Hayakawa went down with Shimakaze, and of the various ship’s crews, about 1,000 sailors were killed.

The 'TA-5' convoy departed Manila on 23 November for Port Cataingan and Port Balancan. Of the six transports, five (T-111, T-141, T-160, T-6 and T-10) were sunk by air attack.

Bad weather late in November made air interdiction less effective, and the US Navy began to send destroyers into Ormoc Bay. The Canigao Channel was swept for mines by the minesweepers Pursuit and Revenge, and the destroyers Waller, Pringle, Renshaw and Saufley of Destroyer Squadron under the command of Captain Robert Smith. The destroyers entered Ormoc Bay on 27 November and bombarded the docks at Ormoc City.

An Allied patrol aeroplane transmitted a message to the division noting that a surfaced Japanese submarine I-46 was south of Pacijan island and heading for Ormoc Bay. The division headed to the south to intercept and, at 01.27 on 28 November, Waller's radar detected the target just off the north-eastern coast of Ponson island. Waller disabled I-46 with her first shots and, unable to submerge, the submarine could return fire only with its deck guns until sinking 01.45.

In the 'TA-6' convoy, the transports Shinsho Maru and Shinetsu Maru, of 4,838 and 2,212 tons respectively, escorted by three patrol vessels in the form of the submarine-chasers No. 45 and No. 53 and Patrol Boat No. 105 departed Manila on 27 November. They were attacked by US PT-boats in Ormoc Bay on the night of 28 November and by air attack as the survivors left the area. All five ships were sunk, but not before they had been able to unload most of their badly-needed supplies to the troops on Leyte island.

Another US destroyer sweep on the night of 29/30 November in search of a reported convoy resulted only in the destruction of a few barges.

The 'TA-7' convoy of three transports departed Manila on 1 December, escorted by the destroyers Take and Kuwa under the command of Lieutenant Commander Masamichi Yamashita. Two groups of transport submarines also took part in the operation. The convoy was docked at Ormoc City when it was attacked from 00.09 on 3 December by the destroyers Allen M. Sumner, Cooper and Moale of Destroyer Division 120 under the command of Commander John C. Zahm. The US warships sank the transports as they were unloading but came under heavy attack from Yokosuka P1Y 'Frances' bombers, shore batteries, submarines that were known to be in the harbour, and the Japanese destroyers. Kuwa was sunk and Yamashita was killed. Take attacked Cooper with torpedoes and escaped, although only after sustaining some damage. Cooper sank at about 00.15 with the loss of 191 men, though 168 others were rescued from the water on 4 December by Consolidated PBY Catalina flying boats. At 00.33, the two surviving US destroyers were ordered to leave the bay, and the Japanese were therefore able to resupply Ormoc Bay once more. This phase of the 'Battle of Ormoc Bay' has gone down in naval history as the only engagement during World War II in which the Japanese brought to bear every type of weapon at their disposal: naval gunnery, naval torpedoes, air attack, submarine attack, shore gunnery and mines.

On 7 December, Major General Andrew D. Bruce’s 77^th Division made an amphibious landing at Albuera, 3.5 miles (5.6 km) to the south of Ormoc City. The 77^th Division’s 305^th, 306^th, and 307^th Infantry came ashore unopposed, but the naval shipping was subjected to kamikaze attacks, resulting in the loss of the destroyers Ward and Mahan.

The 'TA-8' convoy carried 4,000 troops destined for Ormoc Bay, but these were unloaded at San Isidro, 30 miles (48 km) to the north of Ormoc, after receiving news of the US troop landings near Ormoc. All five transports, namely the 4,715-ton Akagisan Maru, 6,650-ton Hakuba Maru, 2,599-ton Shinsei Maru No. 5, 886-ton Nichiyo Maru and T-7, were sunk on 7 December by air attack, and the escorting destroyers Ume and Sugi were damaged. Some 350 Japanese seamen were killed.

The 'TA-9' convoy landed some 4,000 troops at Palompon, on the western coast of Leyte island to the west of Ormoc, but escorting destroyers entered the bay on 11 December where Yuzuki was sunk by air attack and Uzuki was send down by PT-boats), while a third Japanese destroyer, Kiri, was damaged.

This series of engagements in Ormoc Bay eventually made it possible for the US Navy to prevent the Japanese from additional resupply and reinforcement of their troops on Leyte island, contributing significantly to the victory in the land battle. The final tally of US ships lost in Ormoc Bay is three destroyers, one high-speed transport and two medium landing ships, while that of the Japanese was six destroyers, 20 small transport vessels, one submarine, one patrol boat and three escort vessels.