MV Mar Negro was a 6,632-ton motor cargo vessel built in 1930 by the Spanish shipbuilder company Eskalduna in Bilbao. She was part of a series of four ships owned by the Compañía Marítima del Nervión, featuring two sister ships—Mar Cantábrico and two steamers, Mar Blanco and Mar Caribe. Unlike her steam-powered sisters, Mar Negro was propelled by two diesel engines, making her a notable example of early diesel maritime engineering. The vessel measured approximately 132 meters in length and was designed for trade routes between Spain and U.S. ports in the Gulf of Mexico. Initially, Mar Negro served as a commercial cargo ship engaged in international trade. However, with the outbreak of the Spanish Civil War in 1936, she was moored in Barcelona and converted into a troop transport for the Republican side. She participated in the abortive 1936 landing on Mallorca and later became involved in maritime traffic between the Soviet Union and the Spanish Republic. During her Republican service, she survived an attack by an Italian submarine. In September 1937, Mar Negro was diverted to Cagliari, Sardinia, where she was seized by Nationalist sympathizers. After her capture, she was converted into an auxiliary cruiser at her birthplace shipyard, fitted with an array of armaments including four 152 mm Vickers guns, four 88 mm, four 47 mm Armstrong guns, and additional smaller caliber weapons. Completed in May 1938, she joined the Nationalist fleet and served in enforcing blockades, capturing Greek steamers, and shelling Republican-held ports such as Palamós. Mar Negro was involved in notable actions, including the seizure of British merchant ships Stangate and Stanhope during blockade operations off Valencia in 1939. Her career also included a brief incident with the British cruiser HMS Sussex, involving the boarding and capture of the Stangate. She played a vital role in the evacuation of Republican troops from Gandía and participated in the political and military events during the final days of the Spanish Civil War. After the conflict, she returned to civilian service in October 1939, operating between Spain and North American ports until she was partially destroyed by fire in 1962. Rebuilt and renamed several times, she ultimately was scrapped in Taiwan in 1973, marking her as a vessel of both wartime significance and post-war maritime history.

This description has been generated using GPT-4.1-NANO based on the Vessel's wikidata information and then modified by ShipIndex.org staff.