After conducting the world’s first aerial bombardment from an airplane in November 1911 during the Tripolitan War against the Turks, the Italians were quick to recognize the potential for bombers. Indeed, Giulio Douhet’s Rules for the Use of Aircraft in War, published in 1912, specifically called for the development of aircraft capable of dropping heavy bomb loads on enemy targets. Partly in response to Douhet’s book, Giovanni Caproni began developing a large multiengine aircraft. His first attempt, the Caproni Ca 30 biplane, was successfully demonstrated in 1913. Its central nacelle housed three 90 hp Gnome rotary engines, of which the front two used a gear system to power two tractor propellers on booms that extended from the fuselage, whereas the rear motor powered a pusher propellor at the back of the nacelle. This arrangement proved to be underpowered and awkward to operate, leading Caproni to alter his design by using three 100 hp Fiat A. 10 inline engines, two of which were housed on the booms outside the fuselage and powered the tractor propellers directly, whereas the other was housed in the rear of the nacelle and powered a pusher propeller. This prototype, known as the Ca 32, was successfully demonstrated in October 1914.
After Italy entered the war in May 1915, the Italian military quickly placed orders for the Ca 32 prototype, which received the military designation as the Ca. 1 type. It had a wingspan of 72 ft 10 in., a length of 35 ft 9 in., and a loaded weight of 7,280 lbs, including up to 1,000 lbs of bombs that were held in racks under the nacelle. Its three 100 hp Fiat A. 10 inline motors provided a maximum speed of 72 mph, a service ceiling of 4,000 m (13,123 ft), and a range of 344 miles. The Ca. 1 carried four crewmen, including a front gunner and tail gunner who operated two to four ringmounted Revelli machine guns. The tail gunner had to stand in a raised cage from the back of the nacelle in order to fire above the arc of the propeller. Its wooden frame was covered with fabric and thin aluminum sheets protected the nacelle. Its landing gear consisted of two wheels that were attached by struts to the lower wing and two wheels that were suspended from the nose section of the nacelle. It was also distinctive with its twin booms that connected the nacelle and wings to the tail section, which used three rudders. The Ca. 1 began arriving at the front in early August 1915. A total of 166 entered service before production ended in December 1916. During this same period a total of 9 Caproni Ca. 2 biplane bombers also entered service. These were similar in all respects to the Ca. 1 with the exception that they were powered by two 100 hp Fiat A.10 inline engines and one 150 hp Isotta-Fraschini V. 4B Vtype engine.
In late 1916 Caproni introduced his third series of bombers, the Ca. 3 biplane, which used the same airframe and landing gear as the Ca. 1 and Ca. 2. It was powered by three 150 hp Isotta-Fraschini V. 4B V-type motors, which increased its maximum speed to 86 mph and gave it an endurance of 3.5 hours. The added power enabled the Ca. 3 to carry a bomb capacity of 1,760 lbs, which increased its total loaded weight to 8,400 lbs. It had a good climbing rate, which was an absolute necessity in the mountainous regions of the Italian Front, and had a service ceiling of 4,850 m (15,912 ft). Like the earlier Caproni bombers, the Ca. 3 was well protected with two to four ring-mounted Revelli machine guns that were operated by a forward gunner and a tail gunner. In addition to its service as a bomber, the Ca. 3 was also used as a torpedo bomber by the Italian Navy, which operated them out of coastal naval air stations. A total of 269 were produced in Italy between late 1916 and early 1918, eventually equipping 18 squadrons. Approximately 60 were licensed-produced in France by Établissements D’aviation Robert Esnault-Pelterie. Many of the Ca. 3s that survived the war were adapted for mail and passenger service afterward.
In late 1917 Caproni introduced the Ca. 4 bomber, which employed a unique triplane configuration. It had a wingspan of 98 ft (all three wings were of equal length), a length of 43 ft, and a loaded weight of 14,330 lbs, which included a bomb load of 3,000 lbs. The nacelle was attached to the central wing and provided seating for two pilots and a front gunner, who sat in the nose and operated two ring-mounted Revelli machine guns. A tail gunner was placed in each of the twin booms and was provided with one ring-mounted Revelli machine gun, making for a more comfortable arrangement than the standing position required in the earlier Capronis. The first few Ca. 4 triplanes were powered by three 200 hp Isotta-Fraschini V-type engines, but these proved to be underpowered for such a heavy aircraft. As a result, most of the 38 Ca. 4s that entered service were powered by either three 270 hp Isotta-Fraschini V-type motors or three 270 hp Fiat inline motors (a few were also powered by three 270 hp Liberty V-type engines). As in the earlier Capronis, two engines were placed in the forward part of the booms and one was placed in the rear of the nacelle. With performance varying with each engine type, most sources report an average of 87 mph and a service ceiling of 3,000 m (9,843 ft).
The final Caproni bomber of the war, the Ca. 5 biplane, was introduced in early 1918 and remained in service until 1921. It had a wingspan of 77 ft, a length of 41 ft 4 in., and a loaded weight of 11,700 lbs, including a bomb load of 1,190 lbs. Like the Ca. 4, the Ca. 5 employed a variety of engines, using more powerful ones as they became available. The majority were powered by three 300 hp Fiat A. 12 bis inline motors, two of which were placed in the front of the tail booms in a tractor configuration and one which was placed in the rear of the nacelle. The Ca. 5 had a maximum speed of 95 mph and a service ceiling of 4,570 m (14,993 ft). It was protected by one or two ring-mounted Revelli machine guns in the nose section, and one or two ring-mounted Revelli machine guns in a raised turret of the rear nacelle. A total of 255 were built in Italy and at least 3 were produced in the United States by war’s end.
In addition to its Caproni bombers, Italy, like other powers, used a number of its armed reconnaissance aircraft, such as the S.A.M.L. 1 and 2, the S.I.A. 7B2, and the Pompilio P-types, as light bombers. Italy also drew upon British and French bombers. It should also be noted that Italy had semi-ridge airships at its disposal and used approximately twenty of the M-type for bombing purposes during the course of the war. Indeed, on 26 May 1915, just 3 days after it declared war on Austria-Hungary, Italy used one of its M-type airships to bomb Sebenico. First introduced in 1912, the M-type was manufactured by Stabilimento Construzioni Aeronautiche. Unlike zeppelins, which were constructed with an outer and inner metal framework, and blimps, which used the pressure of the gas to keep their shape, the semi-rigid airships of the M-type utilized a central spine or keel that helped maintain its shape and support the engines and carriages. With a length of 272 ft 3 in., a diameter of 55 ft 9 in., and a gas volume of 473,750 cubic ft, the M-type could carry 2,200 lbs of bombs and reach altitudes of up to 4,570 m (14,993 ft). They were powered by two 250 hp Maybach inline motors, which could produce a maxi mum speed of 43 mph and an endurance of 6 hours.