[5][6] For a brief time 1940–41, as Kungsholm was cruising the Caribbean after war broke out in Europe, the author J. D. Salinger was employed aboard as entertainment director.

[7][8] The ship, under the command of Captain John Nordlander, was requisitioned effective 31 December 1941, placed under control of the United States Government's War Shipping Administration (WSA), renamed John Ericsson and delivered for contract operation by United States Lines as a troop transport largely to meet Army requirements.

[9][10] John Ericsson was one of seven transports hurriedly assembled in New York and sailing late on 22 January 1942 (23 January GMT) in what was then the largest troop movement attempted, movement of POPPY FORCE, also designated Task Force 6814, under General Alexander Patch to secure New Caledonia (codename POPPY) on the vital South Pacific link to Australia.

[13] John Ericsson was among the group of large, fast troop transports capable of running without escorts, that moved freely among wartime theaters as required.

[14] After the end of World War Two the John Ericsson was placed in the Hudson reserve fleet 28 April 1947 with fire damages estimated at between $500,000 and $1,500,000 to repair and offered for sale by bids 5 May on an "as is, where is" basis.