 On 1 May, her commander was notified of his promotion to "Korvettenkapitän".On 13 May 1943, "U-176" attacked Convoy NC 18 only five miles off the northern coast of Cuba, sinking the 2,249 ton American tanker "Nickeliner", which was loaded with 3,400 tons of ammonia water, and the 1,983 ton Cuban molasses tanker "Mambí".On 15 May, the Cuban merchant ship "Camagüey", and the Honduran "Hanks", both loaded with sugar, sailed from Sagua La Grande, bound for Havana, escorted by the Cuban submarine chasers "CS-11", "CS-12", and "CS-13".