# Operation Substance

Operation Substance was a British naval operation in July 1941 during the Second World War to escort Convoy GM 1, the first of the series from Gibraltar to Malta. The convoy, escorted by Force H, was attacked by Italian submarines, aircraft and MAS boats (Motoscafo armato silurante, motor torpedo boats).

## Convoy

Port Chalmers carried 250 members of the Royal Artillery one light, one heavy anti-aircraft regiment and thirty field guns to strengthen the island against airborne assault. Medical personnel expected to be needed in the anticipated Siege of Malta were also embarked.
Force H included the battleship HMS Nelson, the battlecruiser HMS Renown, the fast minelayer HMS Manxman, the cruisers HMS Manchester, Edinburgh and Arethusa with eight destroyers and the aircraft carrier HMS Ark Royal with 21 Fairey Fulmar fighters and ferrying seven Fairey Swordfish reinforcements to Malta.

## Prelude

The Royal Navy observed a decrease in the intensity of Regia Aeronautica (Italian Royal Air Force) attacks as the stock of torpedoes at Sardinian airfields was nearly exhausted. The ships of Convoy GM 1 sailed from the British Isles on 13 July 1941 as part of Convoy WS 9C (Winston Specials) and arrived at Gibraltar on 20 July. Ships of the Mediterranean Fleet operating from Alexandria began making much radio traffic to divert attention from Gibraltar towards preparations for a big operation in the eastern Mediterranean. Eight Allied submarines were deployed off Italian naval bases but Supermarina, the Italian naval headquarters, assumed the convoy was Ark Royal flying-off replacement aircraft to Malta and chose to remain in port. Leinster ran aground while leaving Gibraltar on 21 July and had to return to port. The Perla-class submarine Diaspro found the convoy on 22 July and launched torpedoes which narrowly missed Renown and HMAS Nestor.

## Battle of 23 July

The convoy was attacked by nine Savoia-Marchetti SM.79 torpedo bombers coordinated with five CANT Z.1007 medium bombers. Four Fulmars met the torpedo attack head-on and shot down a SM.79 but another SM.79 dropped a torpedo before it was shot down, which hit Manchester. Ark Royal launched seven more Fulmars which were unable to engage the high level bombers before they bombed but these failed to hit the merchant ships; three Fulmars were shot down. A later attack by two SM.79s sank Fearless killing 35 of her crew. Another bombing near-missed Firedrake causing severe damage and the destroyer had to be towed back to Gibraltar. Bristol Beaufighters from Malta reinforced the Ark Royal Fulmars.
Cossack detected the torpedo-boats MAS 532 and MAS 533 approaching the convoy after dark but was unable to prevent them from torpedoing SS Sydney Star (11,000 GRT) at around 03:00 on 24 July. The merchant ship, carrying 484 army officers and men as passengers along with the crew, came to a dead stop as it took on water. Fearing that the ship's pumps were unable to cope with the damage, the captain requested evacuation of the troops. Nestor came alongside and took on board approximately 500 men via gangplank and Jacob's ladder, leaving the captain and a skeleton crew on board. The captain later estimated that his ship had taken on 7,000 long tons (7,100 t) of water. Nestor towed it to Malta, arriving at Grand Harbour shortly after 08:00.

## Aftermath

Seven unloaded ships sailed from Malta in Convoy MG 1 on 23 July to be convoyed back to Gibraltar by Force H. One was damaged by a torpedo bomber on the voyage west. Ark Royal lost six Fulmars defending Convoy MG 1 and the Malta-bound ships from Gibraltar and at least 12 Axis aircraft were destroyed by FAA fighters and the AA guns of the Royal Navy. The six merchant ships of Convoy GM 1 arrived in Malta on 24 July where they were observed by a CANT Z.506 reconnaissance seaplane, escorted by 42 Macchi C.200 fighters. Malta sent 22 Hurricane fighters to intercept, which shot down three of the escort without loss.

### Subsequent operations

The Raid on Grand Harbour, an audacious attack by the elite Decima MAS, using explosive motor-boats (MTM) and manned torpedoes early on 26 July was thwarted by Radar and Ultra, ending in disaster for the Italians.