Her first war patrol began on March 19, 1945. She refueled
at Saipan, then headed for an area south of Bungo Suido (Bungo
Straits). On April 11, Lionfish narrowly evaded two torpedos
fired at her by a submerged Japanese submarine. Twenty days
later she battle-surfaced on a 100-ton schooner and quickly reduced
it to a flaming hulk. From there whe took up lifeguard duty
off of Shanghai, China. On May 9, she rendezvoused with
the USS Ray and took aboard a group of B-29 survivors and deposited
them at the base in Saipan. After topping off with fuel,
she headed for Midway to be refitted, arriving on 22 May 1945.
Lionfish initiated her second foray into the war zone on 20 June
under the direction of Cdr. Bricker Ganyard, again bound for Bungo
Suido. On 10 July she ambushed and torpedoed an I-class
Japanese submarine. After regaining periscope depth, her
captain saw only a cloud of smoke in the direction of her victim.
Shortly afterward, Lionfish's crew heard loud breaking-up noises
and felt confident that the sub had been sunk (this could not
be positively confirmed from postwar records).
In a matter of days, Lcdr Spruance launched similar attacks on
two more enemy submarines. Both failed, one due to an erroneous
TDC setting. With no torpedoes left, she was assigned lifeguard
duty until July 18, when she departed for Tanapag Harbor, Saipan
for more fuel and torpedoes.
She departed Saipan on 22 July and ventured forth to resume lifeguard
duty off the Nansei Shoto and Honshu, Japan. She remained
in this area until hostilities ended on 15 August, then headed
for Midway, arriving on August 22, 1945. Eight days later,
Lionfish left for the West Coast, arriving at Mare Island.
She was decommissioned on 16 January and entered the Pacific Reserve
Fleet. Lionfish was awarded one battle star for her valarous
World War II service.