Aikoku Maru and Hōkoku Maru on 5, 10, and 15 May 1942. I-10′s Yokosuka E14Y1 (Allied reporting name "Glen") floatplane began reconnaissance flights over ports in South Africa by reconnoitering Durban on 20 May 1942, where its crew found no targets of importance. Although challenged from the ground during the flight, the aircraft escaped after its radioman bought time by transmitting a false recognition signal in response. The plane made flights over East London, Port Elizabeth, and Simon's Town over the next week, and by 24 May the "A" detachment submarines were encountering heavy Allied shipping traffic as they approached East Africa. On the night of 29 May, I-10′s floatplane flew over Diego-Suarez, Madagascar, sighting the British battleship among the ships anchored there. The "A" detachment commander selected Diego-Suarez as the target for a midget submarine attack, scheduled for 30 May 1942. On 30 May 1942, I-18′s midget submarine could not launch because of engine failure, but I-16 and I-20 both launched their midget submarines to attack the Allied warships at Diego Suarez. I-20′s midget submarine, M-20b, managed to enter the harbor and was attacked with depth charges, but fired two torpedoes. One torpedo seriously damaged Ramillies, while the second sank the 6,993-ton oil tanker British Loyalty. Ramillies required repairs in South Africa and England. Neither midget submarine returned, and on 31 May 1942, I-10′s floatplane made a flight over Diego Suarez in the hope of locating any of the midget submarine crewmen who might have reached shore, without success. I-16′s midget submarine disappeared at sea and the body of one of its crewman was found washed ashore on Madagascar on 31 May. The crew of M-20b beached their craft at Nosy Antalikely and moved inland towards a pre-arranged pick-up point near Cape Amber, but were both killed in a firefight with British Royal Marines on 2 June 1942; one Marine was killed in the action as well. After the midget submarine attack, the "A" detachment began anti-shipping operations in the Indian Ocean. I-10 had her first success at 02:31 on 5 June 1942 when she sank the 2,639-gross register ton Panamanian steamer in the Mozambique Channel east of Beira, Portuguese East Africa, at . Later that day, she sank the American 4,999-gross register ton armed cargo ship at ; the British steamer rescued Melvin H. Baker′s crew. Again in the Mozambique Channel east of Beira, she torpedoed the 5,224-gross