... In the mid-1930s the Luftwaffe was building up its strength with a number of new warplanes, and the Messerschmitt Bf 110 was the company's submission for a twin-engine fighter for which Focke-Wulf and Henschel also prepared designs. They were to be initially heavy fighters, but with the capability of being deployed as high-speed bombers. Changes in requirements for the fighter resulted in Messerschmitt being the only candidate and three prototypes were built, the first flying on 12 May 1936.

The two 910-hp (679-kW) Daimler-Benz DB 600A engines were very unreliable; nevertheless, a speed of 314 mph (505km/h) was recorded during tests and the general performance was considered reasonable, although swing during take-off and landing gave problems. Engine unreliability plagued the three prototypes, and the pre-production series of Bf 110A-0 aircraft had 680-hp (507-kW) Junkers Jumo 210Da engines which produced a considerable performance penalty, but Messerschmitt was still awaiting the new DB 601A with fuel injection and other improvements. This engine's gestation period stretched even longer, with consequent delays to the Bf 110 program, and after the fourth pre-production aircraft had been completed in March 1938 the company switched to the Bf HOB, a cleaned-up version with provision for two 20-mm FF cannon in the nose, supplementing the four machine-guns carried by the Bf 110A-0. A total of 45 Bf HOBs was built, all with Jumo engines: most were Bf HOB-1 aircraft, but some Bf HOB-2 machines had their cannon removed and cameras installed, while the few Bf HOB-3 examples were earlier aircraft modified subsequently for use as trainers.

DB 601A at last became available, resulting in the Bf HOC with some minor airframe changes, including squarer-cut wingtips and new radiators. Ten Bf 110C-0 pre-production aircraft were delivered for evaluation in January 1939, followed closely by Bf 110C-1 production fighters. As production built up, Focke-Wulf and Gotha joined the program and by the end of August 1939 159 Bf 110Cs had been delivered at a production rate of 30 per month. By the end of the year deliveries had reached 315.

The new fighter proved its abilities in the Polish campaign and in December 1939 succeeded in destroying nine out of 24 Vickers Wellingtons on a mission over the Heligoland Bight. Three other Wellingtons failed to return from this operation and the 50 per cent loss to Bomber Command was a severe blow, but it enhanced the prestige of the Bf 110 as a bomber destroyer.

The high priority afforded to Bf 110 production is reflected in the monthly average of more than 102 aircraft in 1940, but it was in this year, when the Bf 110s began to encounter single-engine fighter opposition, that its shortcomings became apparent, an ominous foretaste of things to come later in the year. While its ability as a day fighter may have been doubted, even in the improved Bf 110C-2 and Bf 110C-3 versions, there were plenty of other roles where it could perform useful tasks.

The Bf 110C4 with armour for the crew and uprated 1,200-hp (895-kW) DB 601N engines was used as a fighter-bomber and could carry two 551-lb (250-kg) bombs beneath the centre section; in this role it became the Bf 110C-4/B and operated against British shipping in the English Channel in the summer of 1940 with success. The Bf 110C-7 was an improved fighter-bomber with up to 2,205 lb. (1000 kg) of bombs, while the Bf 110C-5 was a reconnaissance machine...