Operation Substance

Part of the Battle of the Mediterranean of World War II

Date	11-28 July 1941
Location	Mediterranean Sea
Result	British victory

Belligerents

United Kingdom

Australia

Italy

Commanders and leaders

James Somerville

Unknown

Strength

1 battleship
1 battlecruiser
1 aircraft carrier
4 light cruisers
18 destroyers
13 merchant ships

3 torpedo boats
1 submarine
4 MAS boats

Casualties and losses

1 destroyer sunk
1 light cruiser damaged
1 destroyer damaged
2 merchant ships damaged
6 aircraft

12 aircraft

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 defended by Force H was attacked by Italian submarines, aircraft, and Motoscafo armato silurante (MAS torpedo boats).

The convoy of six cargo ships carried one light and one heavy anti-aircraft regiment with 30 field guns to strengthen the island against possible airborne assault. Medical personnel expected to be needed in the forthcoming siege were also embarked.

Force H included the battleship HMS Nelson, the battlecruiser HMS Renown, the fast minelayer HMS Manxman, cruisers HMS Manchester, Edinburgh and Arethusa with eight destroyers and the aircraft carrier HMS Ark Royal operating 21 Fairey Fulmars and carrying seven Fairey Swordfish to be flown off as reinforcements to Malta.

The Royal Navy observed decreasing intensity of Regia Aeronautica attacks as the torpedo inventory 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 (Winston Specials) 9C, and arrived at Gibraltar on 20 July. Ships of the Mediterranean Fleet operating from Alexandria began making heavy radio traffic in the hope of diverting attention to possible preparations for a major operation in the eastern Mediterranean. Eight Allied submarines were deployed off Italian naval bases; but the Italian fleet assumed the convoy was merely 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.

...
Wikipedia