After fitting out and training, John Penn began preparations for what was to be one of the largest overseas expeditions ever undertaken, Operation Torch, the North African Invasion.

As a unit of Rear Admiral Monroe Kelly's Northern Attack Group she arrived 8 November in the transport area off Mehdia, Western Morocco, where she began landing troops and putting cargo ashore.

John Penn departed Norfolk 17 December for deployment to the Pacific, arriving New Caledonia via the Canal Zone 18 January 1943.

After debarking her grateful passengers at Noumea, New Caledonia, she spent the next six months delivering supplies, equipment, and troops to Guadalcanal from the New Hebrides, the Fiji Islands and New Zealand.

At the time of the torpedoing, Captain Harry William Need (later Rear Admiral) commanded USS John Penn.

In her naval service, the transport had played a key role in the assault and occupation of French Morocco and contributed greatly to the struggle for Guadalcanal.