with were assigned to the Red Sea base of Massawa in Eritrea. In the spring of 1939 Gemma and performed a cruise in the Indian Ocean to test the performance of the class in terms of sailing and operational capability in warm seas and during the monsoon season. The results were disappointing: it was discovered that stormy sea prevented the use of submarine's armament and made it very difficult even to remain at a periscope depth. There were also reports of malfunctioning air conditioning system, and leaks of chloromethane were reported. In the fall of 1939 she came back to the Mediterranean and was assigned to the 14th Submarine Squadron (I Submarine group) based at La Spezia. In 1940 Gemma was reassigned to the 13th Submarine Squadron (I Submarine Group), but was operating from Leros. After Italy's entrance into World War II, Gemma, under command of Guido Lanza Cordero di Montezemolo, was sent to patrol off Chios. She returned to her base on June 15 without encountering any traffic. From June 30 through July 8, 1940 Gemma patrolled off Sollum, and returned to her base without sighting any enemy ships. From August 7 through August 16, 1940 she patrolled off Crete, but again without any success. On September 30, 1940, Gemma sailed to her area of operation, located in the northern section of the Strait of Kasos, just east of Crete. was deployed to the south of Gemma, in the center of the Strait of Kasos, and further south, another submarine, under command of captain Alberto Avogadro di Cerrione, was deployed. Gemma arrived in the area on October 1 and was supposed to remain on station until October 8, but in the evening of October 3 she was ordered to patrol further east in the strait between Rhodes and Karpathos. On October 6, a new order was sent to Gemma telling her to return to the base, but due to a mix-up the message was never received by Gemma and she remained on her station. On October 7, Tricheco had a sick crew on board and had to return to Leros. On her return voyage she had to pass near the eastern coast of Karpathos, thus crossing an area where Gemma was stationed. Due to a mix-up and delay in communication, Tricheco was unaware of Gemmas location. At 1:15 on Oct. 8, Tricheco sighted in the dark a silhouette of