'Supply' was an Allied naval anti-submarine patrol undertaking off Madagascar (1941).

In the period before their 'Ironclad' invasion of the Vichy French island of Madagascar, the British feared that the Japanese, building on the concessions which they had been able to wring from Vichy France for the occupation of Indo-China, might bring a similar pressure on Vichy France and gain a foothold in Madagascar, if only for the basing of submarines.

The need for such patrols was in fact revealed by the fact that the Japanese attempted a submarine intervention against the British naval forces involved in the 'Ironclad' operation against the Vichy French island of Madagascar in May 1942. The Japanese submarines I-10, I-16 and I-20 arrived on 29 May, and I-10's reconnaissance floatplane spotted the British battleship Ramillies at anchor in Diégo Suarez harbour. The floatplane was seen, however, and Ramillies changed her berth.

I-20 and I-16 each launched a midget submarine, one of which managed to enter the harbour and fire two torpedoes while under depth charge attack from two corvettes. One of the torpedoes seriously damaged Ramillies, while the second sank a tanker, British Loyalty, which was later refloated. Ramillies was later repaired in Durban and Plymouth.

Lieutenant Saburo Akieda and Petty Officer Masami Takemoto beached their midget submarine at Nosy Antalikely and moved inland toward their designated pick-up point near Cape Amber. They were reported when they bought food at a village, however, and both were killed in a firefight with Royal Marines three days later.

The second midget submarine was lost at sea and the body of one its crew was washed ashore a day later.