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.

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.

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.

Asakaze and Yūnagi were detached to escort the damaged ship back to Takao as a typhoon developed with force 12 winds from the southeast.

[citation needed] Picuda and Spadefish were unable to locate the convoy in the deteriorating visibility, and heavy seas loosened plates on the superstructure of Redfish.

[citation needed] 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.

[citation needed] Rasher launched four bow torpedoes shortly after midnight at a range of 2,200 yards (2,000 m), and three hits on the cargo-transport Eishin Maru[3] caused an ammunition detonation with the pressure wave sweeping over the submarine's bridge.

[2] Both torpedoes hit at 0033[citation needed] and Noshiro Maru[3] slowed to 5 knots (9.3 km/h) reversing course[2] and firing briefly at Etorofu believing it to be the attacking submarine.

[citation needed] 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.

[citation needed] Asakaze and Yūnagi departed Takao on 21 August to rejoin the convoy at Manila with the new tankers Hakko Maru No.

[citation needed] 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.