1941 Onice was assigned to Benghazi to conduct daily anti-submarine patrols to protect convoys from and to Libya. During the night of October 1, Onice was on an anti-submarine patrol in an anticipation of arrival of a German convoy coming from Naples and heading to Benghazi. The convoy consisted of steamers Savona and Castellon, escorted by torpedo boats Calliope and Pegaso and was expected to arrive in the morning of October 2. Patrol boats Zuri and Selve were also on patrol as the Benghazi navy command believed there were British submarines hiding outside Benghazi harbor. Onice left the area shortly after midnight while Zuri and Selve continued their search until the arrival of the convoy. Despite much effort by the Italians, at 10:12 on October 2 British submarine Perseus was able to attack and sink steamer Castellon. On October 10, 1941, while surfaced she exchanged torpedo attacks and gunfire with a British submarine, but the combat was inconclusive. On October 14, 1941 Onice was reassigned to Messina. For the rest of the year she was involved in several patrols in the Strait of Sicily with no results. On January 3, 1942, she was deployed to patrol an area south-southeast of Malta with the task of detecting and attacking any British naval forces that would have tried to intercept a large supply convoy M. 43 to Libya, but she didn't sight any British vessels. On March 11, 1942, Onice under command of captain Bruno Zelik was sent to patrol in the Eastern Mediterranean, and stayed on patrol until March 27. On March 16, while patrolling off Cape dell'Armi, she was attacked by British submarine P-36 who launched two torpedoes. Onice maneuvered to avoid being hit and counterattacked by also launching torpedoes and opening fire with the deck gun forcing the enemy submarine to dive and retreat. At 17.45 on March 21, 1942 Onice, while on patrol southwest of Cape Krio, sighted in the position a group of unknown ships moving north-northwest. Due to high wind and rough seas Onice struggled to stay at the periscope depth or even identify the type of sighted vessels. At 17:47 she radioed a discovery message to Supermarina which was received at 20:00. The ships sighted by Onice were part of the MW10 convoy, traveling from Alexandria to Malta with urgent supplies for the garrison of the island. There were three cargo ships (Clan Campbell, Pampas