HMS Illustrious

The Illustrious class was born from a hard strategic truth the Royal Navy faced in the 1930s. Unlike the Americans and the Japanese, Britain expected to fight its carriers within reach of powerful land-based air forces — in the North Sea and the narrow Mediterranean — where a wooden flight deck packed with fuelled aircraft was a floating bomb. Ordered under the 1936 and 1937 Programmes, Illustrious was designed around a radical protective idea and commissioned on 25 May 1940, just as the war in the West exploded into life.

Her designers made a choice no other navy would: they wrapped the hangar in armour and armoured the flight deck itself, accepting a far smaller air group in return. Where a contemporary American carrier might embark 80–90 aircraft, Illustrious carried around 36 — the price of turning the vulnerable heart of a carrier into an armoured box. It was a bet that survival mattered more than numbers, and within a year it would be tested more brutally than her designers can ever have imagined.

Illustrious displaced about 28,600 tonnes at full load on a hull roughly 226 m long, with machinery of some 111,000 shp giving about 30.5 knots. Her defining feature was 76 mm (3 inches) of armour over the flight deck and 114 mm armoured hangar sides, forming a closed armoured box meant to keep bomb splinters, blast and fire away from her aircraft and their petrol. The single enclosed hangar that resulted was the very reason her air group stayed so small.

For a ship expected to fight under air attack, her own anti-aircraft battery was correspondingly heavy: sixteen 4.5-inch (114 mm) dual-purpose guns in eight twin turrets, backed by multiple eight-barrelled 2-pounder “pom-poms.” Everything about the design assumed the carrier herself, not merely her aircraft, would be in the firing line — a philosophy the rest of the naval world thought eccentric until the war proved it right.

On the night of 11–12 November 1940 Illustrious launched the strike that changed naval warfare. Under Admiral Andrew Cunningham’s Mediterranean Fleet she flew off 21 obsolescent Fairey Swordfish biplanes in two waves against the Regia Marina’s main base at Taranto — Operation Judgement. Their torpedoes, specially modified to run in the harbour’s shallow water, struck the anchored Italian battle fleet, sinking or crippling three battleships: the Conte di Cavour, which never returned to service, and the badly damaged Littorio and Caio Duilio.

For the loss of just two aircraft, a handful of biplanes had halved Italy’s battle line in a single night and forced the Regia Marina to withdraw its heavy ships north to Naples. It was the first time a fleet had been decisively struck in harbour by carrier aircraft alone, and the lesson was not lost on the Imperial Japanese Navy, whose officers studied Taranto closely as they refined the plan for Pearl Harbor a year later.

Taranto brought retribution. In January 1941 the Luftwaffe’s specialist anti-shipping command, Fliegerkorps X, arrived in Sicily hunting the carrier that had humiliated the Axis. On 10 January, south of Malta, waves of Ju 87 Stukas and Ju 88s concentrated on Illustrious and hit her with around six bombs of 500 kg and heavier, wrecking her hangar, jamming her steering and killing 126 of her crew.

That she survived at all was the armoured box vindicated — damage that would almost certainly have sunk an unarmoured carrier. She clawed her way into Malta’s Grand Harbour, endured days of further bombing that Maltese remember as the “Illustrious blitz,” then slipped out to Alexandria and steamed on, by way of the Cape and the Panama Canal, to the Norfolk Navy Yard in Virginia, where American shipwrights spent most of 1941 rebuilding her.

Repaired and modernised, Illustrious returned to a war utterly transformed by carrier air power. From 1944 she fought with the Eastern Fleet in the Indian Ocean, her air group now a modern mix of some 57 Vought Corsairs and Grumman Avengers. Alongside the American carrier USS Saratoga she struck the Japanese-held harbour of Sabang on 19 April 1944 and the oil refineries of Surabaya on 17 May — among the first times British and American carriers operated together against Japan.

These were the operations of a mature fleet air arm, ranging across an ocean the Royal Navy had nearly lost in 1942. But the hardest test of her armoured deck still lay ahead, in the skies over the last great battle of the Pacific war.

In 1945 Illustrious joined the British Pacific Fleet — Task Force 57 — for Operation Iceberg, the invasion of Okinawa, flying strikes to suppress the Japanese airfields of the Sakishima Islands. Here she met the kamikaze. On 6 April 1945 a suicide aircraft was shot down so close that it exploded against her side, and across her class the armoured decks shrugged off hits that gutted American carriers built with wooden decks.

The contrast became legend in the US Navy, where a liaison officer’s verdict was widely quoted: when a kamikaze struck an American carrier it meant six months in a repair yard; when one struck an armoured British carrier, the signal was simply “Sweepers, man your brooms.” Worn out by five years of hard steaming and accumulated battle damage, Illustrious was sent home in 1945, ending her days as a trials and training carrier before she was scrapped in 1956.

HMS Illustrious embodied a distinctly British answer to the central problem of carrier design: protection over numbers. The choice cost her striking power throughout her career, but it kept her alive through punishment few carriers of any navy could have survived, and it delivered at Taranto one of the most influential air strikes in the history of war at sea.

Her ideas outlived her. The armoured flight deck, thought eccentric in 1940, was vindicated so completely by the kamikaze that it shaped post-war carrier design around the world. From the Mediterranean to the Pacific, Illustrious left a mark on naval warfare out of all proportion to her modest air group — a ship whose ideas were proven right under fire.

• Roger Chesneau (ed.), Conway’s All the World’s Fighting Ships 1922–1946 (Conway Maritime Press).
• David Hobbs, British Aircraft Carriers: Design, Development and Service Histories (Seaforth).