hit amidships and aft by two torpedoes, while Venore, 20 miles behind, had only one torpedo hit that set her boilers on fire. U-66 then continued eastward back to Lorient, where she arrived on 10 February. Fifth On 21 March, U-66 left for what proved to be her most successful patrol, resulting in 43,956 gross metric tons sunk and 12,502 gross metric tons damaged in the Caribbean Sea. 24 days after departure she sank Korthion, a Greek steam merchantman just south of Barbados with one torpedo hit amidships. Two days later, the boat sank Amsterdam, a Dutch steam tanker, which split in two after being hit by two torpedoes, one amidships, and one in the engine room. Most of the survivors were picked up near Port of Spain, (Trinidad) by Ivan, a Yugoslavian steam merchant vessel. The next day U-66 attacked Heinrich von Riedemann, an 11,020 GRT Panamanian motor tanker. The first torpedo severely damaged the steering control of her port engine and ruptured a tank of oil, making much of it leak out. 20 minutes after the first hit, just after the starboard engine was stopped, the ship was abandoned when the crew took to the lifeboats. An hour later U-66 hit her with a second torpedo, setting her afire. It extinguished itself within 25 minutes. 50 minutes later the submarine hit her with a third torpedo, which set the ship afire again. She remained that way for about 70 minutes before she finally sank. Nine days later U-66 sank the US Alcoa Partner with a torpedo and a shot from her deck gun. Sixth After her fifth patrol, Richard Zapp left U-66 to take command of the 3rd U-boat Flotilla. This meant that Kapitänleutnant Friedrich Markworth was in charge. The submarine started her sixth patrol with the sinking of Triglav, a Yugoslavian steamer, after depositing a sick crew-member in Spain. After a couple of weeks, U-66 ran across the 4,942 GRT Brazilian merchant ship Tamandaré, sinking her with a torpedo hit in her stern. The survivors were picked up by the . Two days after the attack on Tamandaré, U-66 sank Weirbank, a British merchantman on 28 July 1942, with the second of two torpedoes launched at her. Four days after her previous sinking, two mines from U-66 severely damaged two British motor torpedo boats that had left on a patrol from Port Castries, St. Lucia. Those two