In 1926 the vessel was bought by the American-South African Line and for the next fourteen years continuously sailed between the East Coast of the United States and South Africa.

[3] The vessel also possessed all the modern machinery for quick loading and unloading of cargo from five large hatches, including ten winches and eleven booms.

Upon acceptance by the Shipping Board, West Cawthon was allocated to Matson Navigation Company and departed the same day for San Francisco to load cargo for her upcoming trip.

West Cawthon left San Francisco on July 13 and after short stopover at Honolulu for bunkers continued to her final destination arriving at Manila on August 15.

[10] After fighting through a typhoon off Japanese coast for two days, she returned to San Francisco on October 9, successfully completing her maiden voyage.

West Cawthon did not suffer any damages as a result of quick actions undertaken by firefighters and was able to depart on her second voyage to the Far East two days later.

[13] In early December 1919, while still en route, West Cawthon was sold by USSB to the Imperial Shipping Corporation, a wholly owned subsidiary of the Green Star Line.

[21] The vessel sailed from Galveston on June 22 laden with 269,000 bushels of wheat and returned to New York from Spezia in ballast on August 18 concluding her first full trip under new ownership.

[29][30] In January 1923 as the sea trade rebounded, West Cawthon was originally allocated to International Freighting Corporation to serve their Philadelphia to ports of River Plate route.

Upon arrival at New York from her last trip on Christmas Day 1923 she was put under control of Mallory Steamship Company who similarly operated a large scale service route to the Mediterranean ports of Italy and Spain.

[35] West Cawthon spent an entire 1924 under Mallory Line control, making several trips from the East Coast of the United States to various ports in the Mediterranean.

Typically, the vessel would carry general cargo to Marseille, Leghorn and Genoa on her eastward journeys, occasionally supplementing it with grain and coke.

On her westward trips she would also carry various general cargoes in addition to some local specialties such as pumice from Lipari, lemons from Sicily and onions from Valencia and Gandia.

The company's goal was to establish and maintain a direct trade route between the United States and the ports of British and Portuguese South Africa.

[39] After repairs and reconditioning, West Cawthon loaded her cargo and sailed from New York on her first voyage under new ownership on 27 March 1926 bound for Cape Town.

For example, she brought in such cargo of wool, hides, chrome ore and whale guano to Boston and Baltimore in November 1927 upon return from one of her regular trips.

In addition to her regular cargo West Cawthon carried exotic animals from Africa for local North American zoos.

This was the first time the aircraft was shipped and delivered in such a manner and was accompanied on this voyage by Opie K. Swope, president of the Beechcraft flying service.

[50] In May 1932 West Cawthon transported a runaway kidnapper, Martin DePew, who kidnapped a wealthy Kansas City woman, Mrs. Nell Donnelly, but managed to escape to South Africa following her release.

In February 1940 she brought into New York $3,000,000 worth of gold from South Africa to establish British credits in the United States to procure war matériel and supplies.

[56] The freighter then loaded a cargo of steel and general merchandise and sailed from Halifax as part of convoy HX-58 on 15 July 1940 bound for Liverpool.

[57] The convoy reached its destination on 31 July, where West Cawthon was officially transferred into British registry, defensively armed with a 4 in (100 mm) naval gun and renamed Empire Bison.

[58] At about 0600 on September 8 while the ship was in approximate position 55°17′N 18°03′W / 55.283°N 18.050°W / 55.283; -18.050, roughly 300 nautical miles (560 km) west of Ireland, Empire Bison was spotted by a German Fw-200 Condor bomber from Kampfgeschwader 40 on a regular reconnaissance and anti-shipping mission.

Not willing to give up, the plane then spent the next half hour continuously strafing Empire Bison from its cannon and machine guns, decimating two lifeboats and riddling every room on the vessel with bullets.

Out of forty two people on board the ship, only three crew members and one passenger managed to survive as they were able to find a raft floating among the debris.