The first effort to sink the "Ciudad de Barcelona" had been attempted in January 1937, but the torpedo had malfunctioned. On Saturday 29 May 1937, some 200–250 international volunteers boarded the ship in Marseille. They were mainly from North America, Great Britain, Germany and Italy, but some came from Scandinavia, Australia and New Zealand. There was also a group of French pilots and Senegalese passengers. "Ciudad de Barcelona" was intended to sail to Barcelona or Valencia, depending on situation of the armed conflict between the communists and anarchists in Barcelona. The ship had a cargo of war material, including items like tanks, tires, motorcycles, cotton fabrics and canned food. A day before, the ship's cargo of flour was sabotaged as someone had poured kerosene upon it. She was under the command of captain Francisco Nadal.