In North Africa, German forces had gone onto the offensive in Operation Sonnenblume. By late April British Army forces were being forced out of Libya and Tobruk was surrounded. Simpson ordered his submarines to intercept convoys sailing from Naples and delivering supplies to the Axis armies in Africa. To assist, Horton formed the 5th Destroyer Flotilla with the light cruiser "Gloucester" as support. Simpson sent "Upholder", "Ursula" and "Upright". Simpson ordered his submarines into action on 27 April and 1 May. On 1 May 1941, "Upholder" and "Ursula" gained contact with a convoy but the ships were travelling too fast to close to effective range. Six hours later he spotted five transports with four destroyers conducting zig-zagging courses to avoid underwater attacks. The water was rough but Wanklyn fired a three-torpedo salvo at the two largest, overlapping, vessels. Three explosions were heard. The German liner "Leverkusen", which had been hit twice, sank by the stern. The third torpedo had stopped "Arcturus", which was listing heavily by the bow. The enemy delivered a moderate counter-attack and sped off. Wanklyn used his final two torpedoes to sink the damaged vessel. The tanker "Bainsizza" was also hit by "Upholder" and sank immediately. The patrol yielded three ships of around 19,000 tons. Simpson immediately recommended Wanklyn and his officers for awards.