Piaggio P.108B

Among the major combatants of the Second World War, Italy stood almost alone in entering the conflict with no true four-engine strategic bomber in service. Regia Aeronautica doctrine, shaped by the theorist Giulio Douhet yet starved of industrial resources, had concentrated on fast twin- and tri-motor medium bombers like the S.79. The Piaggio P.108 was the great exception — Italy's only operational four-engine heavy bomber of the war, and one of the most advanced aircraft the country ever built.

Designed by Giovanni Casiraghi, who had worked in the American aviation industry and brought modern structural thinking back to Piaggio, the P.108 was conceived in the late 1930s as a long-range heavy capable of carrying a substantial bomb load deep into enemy territory. The prototype first flew in November 1939, placing Italy — at least on paper — in the same league as Britain and the United States.

The P.108 was a genuinely modern design, powered by four Piaggio P.XII RC.35 radials of around 1,500 hp each and able to lift some 3,500 kg of bombs over considerable distances. Its most striking feature was its defensive armament: the bomber carried remotely-controlled powered gun barbettes built into the upper rear of the two outer engine nacelles, each mounting twin 12.7mm machine guns and aimed by a gunner from a sighting station in the fuselage.

This was a remarkable innovation. Remote-control powered turrets of this kind would not become widespread until the American B-29 appeared years later, and the P.108's installation marked Italian engineering at its most ambitious. The aircraft also bristled with additional defensive guns in nose, dorsal and ventral positions.

Ambition, however, ran ahead of Italy's industrial capacity. The complex airframe and its advanced systems were difficult to build and maintain, the engines proved troublesome and unreliable, and the whole programme was dogged by delays. Tragedy marked it early: in August 1941 Bruno Mussolini, son of the Duce and an air-force officer, was killed when a P.108 prototype crashed on a test flight.

Several variants were planned around the common airframe. The definitive bomber was the P.108B (Bombardiere), the only version to see real operational service. The extraordinary P.108A (Artigliere) was an anti-ship variant fitted with a 102mm cannon in the nose, intended to attack warships from beyond the range of their anti-aircraft fire — a striking idea that never entered service.

Transport derivatives, the P.108C and P.108T, were also built, the latter used to ferry men and supplies, including service with the Luftwaffe after the Italian armistice. In all, only around 24 P.108B bombers were completed — a tiny number for so significant a type.

The P.108B equipped a single specialised unit, the 274ª Squadriglia of the long-range bombing group, which received its aircraft in 1942. From bases in Sardinia the bombers flew some of the most ambitious missions ever mounted by the Regia Aeronautica, including long-range night raids against Gibraltar — strikes deep into the western Mediterranean that demonstrated exactly the strategic reach the type had been built for.

It was a remarkable machine for Italy — the only four-engined heavy bomber the country put into service, in a class with the Allied heavies. Its development had already cost the regime dearly: Bruno Mussolini, the Duce’s son, was killed test-flying a P.108 prototype in August 1941. The handful that reached service carried the Regia Aeronautica’s only true strategic reach.

The P.108 also flew against targets in North Africa and Allied shipping. But operating so few complex aircraft, plagued by engine unreliability and the chronic shortages of late-war Italy, the squadron could never achieve more than pinprick effect. Losses to accidents and combat steadily thinned the small fleet, and after the September 1943 armistice the survivors were largely grounded or passed to the Germans, chiefly in the transport role.

But a strategic bomber force cannot be built from a single squadron. Complex, thirsty and plagued by unreliable engines, the P.108 could never be maintained or replaced in the numbers strategic bombing demands, and every loss was keenly felt. It remains a might-have-been: the right idea, pursued by an industry that had neither the resources nor the time to see it through.

The Piaggio P.108 stands as a fascinating and frustrating monument to Italian aviation: technically advanced — its remote-control gun barbettes anticipated the B-29 — yet built in numbers so small, and so late, that it could have no real strategic impact. It was the right aircraft for a doctrine and an industry Italy never truly possessed.

As the only four-engine heavy bomber any Axis power in the Mediterranean fielded operationally, and as a showcase of genuine engineering innovation, the P.108 deserves a place larger than its handful of sorties suggests. The scale is the point: Italy completed roughly 24 of them, while Britain and the United States built four-engine bombers in the tens of thousands. That disparity is the clearest single measure of what a strategic air force actually cost.

• Chris Dunning, Courage Alone: The Italian Air Force 1940–1943 (Hikoki Publications).
• Jonathan W. Thompson, Italian Civil and Military Aircraft 1930–1945 (Aero Publishers).
• Giorgio Apostolo, Piaggio P.108 (Ali d’Italia).