After trials and diving tests in Lake Michigan, voyages down the Mississippi, and shakedown out of New Orleans, Icefish joined the Pacific Fleet at Pearl Harbor 22 August.

Assigned to Vice Admiral Charles A. Lockwood's Pacific Fleet Submarines Force, she joined "Banister's Beagle's" (consisting of Comdr.

Alan B. Banister in Sawfish (SS-276) and Drum (SS-228)) and departed 9 September on her first war patrol which took her into Luzon Straits and the South China Sea.

October 1944 was a peak month in the war of U.S. submarines on Japanese shipping: 322,265 tons were sunk, and almost one-third of that total consisted of tankers.

This patrol lasted 43 days with no results and she was forced to return to Pearl Harbor 20 January 1945 due to materiel difficulties.

Her fourth war patrol was conducted in the Hainan, Hong Kong, Formosa, Siam Gulf, and Java Sea areas.

Recommissioned at Mare Island 5 June 1952, Icefish transited the Canal Zone and arrived Groton, Conn., 14 July.