 was one of the World War II Hi convoys of fast tankers and troop transports from Japan to Singapore. The heavily defended convoy was specially loaded with reinforcements for defense of the Philippines, and encountered a wolfpack of United States Navy submarines in the South China Sea after being scattered by an August 1944 typhoon. Personnel losses were high because heavy seas prevented rescue of crewmen from sunken ships.
Background.
Japanese shipping through the South China Sea carried much of the food sustaining the Japanese population, the petroleum fueling Japan's aircraft and warships, and the raw materials for World War II. Japanese aircraft and warships patrolled South China Sea shipping lanes from bases in the Philippines; and loss of those bases would threaten the flow of resources needed to defend the Empire of Japan.
As Allied forces converged to fulfill Douglas MacArthur's promised return, Japan implemented Operation "Shō" to defend the Philippines. Convoy Hi-71 carried Imperial Japanese Army troops, weaponry and supplies from the home islands of Japan to reinforce the Philippines. The convoy left Moji on 8 August 1944 accompanied by the 6th Escort Group of two destroyers and five "kaibōkan" with an escort carrier embarking the 931st Air Group detachment of a dozen Nakajima B5N "Kate" attack planes. As the convoy departed the Mako naval base in the Pescadores on 17 August, it was reinforced by another destroyer and four "kaibōkan" to counter United States submarines operating in the Luzon Strait.
Two submarine wolfpacks were waiting in the convoy path. and operated as "Donc's Devils", under command of Glynn R. Donaho, commanding officer of . The other three submarines were , and .
Battle of 18 and 19 August.
"Redfish" found the convoy on the evening of 17 August, and maneuvered into position to launch four torpedoes at a large ship and a fifth torpedo at the escort carrier. "Eiyo Maru" was hit by a torpedo at 0524 on 18 August. "Asakaze" and "Yūnagi" were detached to escort the damaged ship back to Takao as a typhoon developed with force 12 winds from the southeast. "Picuda" and "Spadefish" were unable to locate the convoy in the deteriorating visibility, and heavy seas loosened plates on the superstructure of "Redfish". The convoy became scattered and disorganized in heavy weather and darkness.
"Rasher" observed nine successive aircraft contacts to the north on the afternoon of 18 August and deduced these were air patrols for an important convoy. That dark, rainy night "Rasher"'s radar picked up thirteen ships of convoy Hi-71 proceeding at and protected by six escorts. After a surfaced approach to , two stern torpedoes were launched at "Teiyō Maru" at 2122. Both torpedoes hit; and the tanker loaded with gasoline exploded into a column of flame high, with parts of the ship being blown from the flaming hulk. The escorts fired wildly and laid depth charge patterns astern of "Rasher". In a second surfaced approach to "Rasher" launched a spread of six bow torpedoes at 2310. Three torpedoes hit and sank the transport "Teia Maru", killing 2,665 Japanese soldiers, and a fourth torpedo was heard exploding at a timed range of 3900 yards. "Rasher" swung hard left to launch four stern torpedoes at 2214. Three torpedoes hit and sank the escort carrier "Taiyō", and the fourth torpedo was heard exploding on a more distant ship.
"Rasher" pulled away to reload torpedo tubes and the convoy split into two groups. "Rasher" followed three large ships with one "kaibōkan" moving northwest while "Bluefish" intercepted the remaining ships continuing southwesterly and fired torpedoes at two tankers. At least one torpedo hit "Awa Maru", and "Hayasui" burst into flame and sank stern first after being hit by two or three torpedoes at 0320.
"Rasher" launched four bow torpedoes shortly after midnight at a range of , and three hits on the cargo-transport "Eishin Maru" caused an ammunition detonation with the pressure wave sweeping over the submarine's bridge. The fourth torpedo was heard exploding on a more distant ship. "Rasher" then swung hard right to launch two stern torpedoes. Both torpedoes hit at 0033 and "Noshiro Maru" slowed to reversing course and firing briefly at "Etorofu" believing it to be the attacking submarine.
Other portions of the scattered convoy were attacked by "Redfish" and "Spadefish". Japanese sources indicate "Tamatsu Maru" simply disappeared. Uncertainty remains about which submarines launched torpedoes striking the ships of convoy Hi-71; but JANAC credited "Spadefish" with sinking "Tamatsu Maru" fleeing northward at 0333. "Sado", "Matsuwa" and "Hiburi" attempted to hold the American submarines down while "Noshiro Maru" and "Awa Maru" beached themselves at Port Currimao to avoid sinking, and undamaged ships took refuge in San Fernando, La Union.
Manila.
After convoy Hi-71 reformed in San Fernando, it arrived in Manila on 21 August. "Awa Maru" was towed into Manila the same day, and "Noshiro Maru" reached Manila on 24 August. "Sado", "Matsuwa" and "Hiburi" were intercepted by and as they attempted to rejoin their convoy in Manila. "Matsuwa" and "Hiburi" were torpedoed by "Harder" at 0456, and "Sado" was torpedoed by "Haddo" at 0524 while attempting to aid the stricken sister "kaibōkan". Additional torpedoes were required to sink the three "kaibōkan". "Haddo" sank "Sado" with a three torpedo salvo at 0720, while "Harder" sank "Matsuwa" at 0649 and "Hiburi" at 0755.
"Asakaze" and "Yūnagi" departed Takao on 21 August to rejoin the convoy at Manila with the new tankers "Hakko Maru" No. 2 and "Niyo Maru" bound for Singapore. "Spadefish" hit "Hakko Maru" No. 2 with two torpedoes off Cape Bojeador Lighthouse at 1455 on 22 August. The damaged tanker was beached in Pasaleng Bay while "Yūnagi" stood by. "Spadefish" fired four more torpedoes at the beached tanker until a depth charge attack by "Yūnagi" chased away the submarine. "Yūnagi" was relieved of responsibility for "Hakko Maru" No. 2 on 25 August and was sunk an hour later by "Picuda". "Hakko Maru" No. 2 remained beached until destroyed by heavy surf on 18 September.
"Asakaze" escorted "Niyo Maru" toward Manila. "Haddo" hit "Asakaze" with its last torpedo at 0800 23 August. As and "Harder" approached to finish off the damaged destroyer (which had already sunk), they were intercepted at 0630 on 24 August by "CD No. 22" and the captured United States destroyer Patrol Boat No. 102. "Harder" fired a salvo of torpedoes at "CD No. 22", and was spotted by a Japanese aircraft which marked the location. "Harder" was sunk at by "Patrol Boat No. 102" in an attack beginning at 0828.
The reformed convoy Hi-71, less the surviving Philippine reinforcements, left Manila on 26 August escorted by "Fujinami", "Hirato", "Kurahishi" and "Mikura", and reached Singapore on 1 September. The unrepaired "Noshiro Maru" remained in Manila Bay until destroyed on 21 September by aircraft of Task Force 38.
Notes.
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