It would perhaps be unkind to describe the Douglas A-20 (company identification DB-7) as undistinguished, especially when it was one of the most extensively built light bombers of World War 11. It was, in fact, an ubiquitous aeroplane, used in a variety of roles, and performing well in that chosen role no matter where it was deployed.

The basic design originated as early as 1936, when the Douglas Aircraft Company began to consider the creation of an attack aircraft which, although un- specified by the US Army Air Corps, would serve as a more effective replacement for the single-engined Model SA, itself derived from the earlier Northrop Model 2-C. By discussion with engineering staff of the USAAC, it became possible to outline a fairly advanced specification, leading to the company project identified as the Model 7A but this, with its twin-engined powerplant, was certainly breaking new ground, for all previous attack aircraft procured by the US Army had been of single-engined layout. There was, however, then no alternative to the twin-engined layout if the suggested performance and gun/weapon-carrying capability was to be achieved, even this was to need revision very shortly, as information began to filter through of the aircraft involved, and their advantages or shortcomings, when large-scale civil war erupted in Spain.

Redesign in 1938 produced the Model 7B, also of twin-engined configuration, but with the then-proposed 450 hp (336 kW) engines replaced by two 1,100 hp (820 kW) Pratt & Whitney R-1830 Twin Wasps. Of cantilever shoulder-wing configuration, the Model 7B had an upswept aft fuselage, mounting a conventional tail unit. Landing gear was of the retractable tricycle type, but a most unusual feature was the introduction of interchangeable fuselage nose sections that would make for easy production of either attack or bomber versions: for deployment in the former role a solid nose housed four 7.62 mm (0.30 in) machine guns, to supplement the standard six 7.62 mm (0.30 in) guns of which two were mounted in a blister on each side of the fuselage, plus one each in retractable dorsal and ventral turrets; and for deployment in the latter role the bombardment nose was conventionally glazed, but had an obliquely-mounted optically-flat bomb-aiming panel. First flown in this form on 26 October 1938, the Model 7B evinced the characteristics of a thoroughbred. It was fast, highly manoeuvrable and, in fact, could be regarded as a 'pilot's aeroplane'.

Immediately the company realised its potential it offered the type for export, as the USAAC then had no requirement for such a machine. The first order, for 100 aircraft, came from a French purchasing mission in February 1939. However, although impressed by the performance of the Model 7B, many modifications were demanded to render the aircraft more suitable for what were considered to be essential requirements for its deployment in Europe, where advanced aircraft in service with the Luftwaffe had demonstrated their potential in the recently ended Spanish Civil War.

So extensive were the modifications that even the basic configuration of the Model 7B was changed, with the fuselage deepened to increase internal bomb capacity and fuel tankage, and its cross-section reduced, thus preventing both navigator/bomb aimer and gunner moving from their operational stations; the wing was lowered from the shoulder-to mid-wing position; a longer oleo-strut for the nosewheel was introduced; provision of armour protection for the crew and fuel tanks was made; and uprated Twin Wasp engines developing 1,200 hp (895 kW) each were installed. In view of the foregoing changes, the resulting aircraft was redesignated DB-7 (Douglas Bomber), and the production prototype was flown for the first time on 17 August 1939. Despite a miraculous effort made by Douglas to complete the manufacture of the initial 100 DB-7s by the end of 1939, the French had only managed to get just over 60 into service at the time of the German attack on 10 May 1940. Of these, only 12 aircraft of Groupement 2 were used operationally, on 31 May 1940, in low-level attacks on German armoured columns.

During the period when Douglas was developing the DB-7, a new French order for an improved version was received. Required to operate at a gross weight about 24 per cent higher than that of the DB-7, as a result of additional equipment, this necessitated the provision of 1,600 hp (1193 kW) R-2600 Wright Cyclone 14 radial engines in revised nacelles, with associated changes in the engine installation, and the revised aircraft was designated DB-7A. Moreover, because the DB-7 had shown that directional stability was bordering on the marginal, even with 1,200 hp (895 kW) engines, increased fin and rudder area was provided to cater for the higher power engines.

When it was clear that the collapse of France was imminent, steps were taken to arrange for the UK to take over the balance of the French orders, plus a small quantity which had been ordered by Belgium. Thus some 15 to 20 DB-7s entered service with the RAF. These were allocated the name Boston 1 and used as conversion trainers in Operational Training Units, including No.13 OTU at RAF Bicester. Most of the Gallic oddities had been ironed out before the aircraft were delivered, but instruments with metric calibration caused a few eyebrows to be raised in horror. The next batch to be received, about 125 DB-7 aircraft, were originally allocated the designation Boston II. However, their load-carrying capability and high speed confirmed a suitability for conversion to desperately needed night fighters, and in the winter of 1940 these were provided with AI (Airborne Interception) radar, additional armour, eight 7.7 mm (0.303 in) machine guns in the nose, flame-damping exhaust systems, and overall matt black finish, under the new designation Havoc 1. One very unusual addition was the provision of basic dual flying controls in the gunner's position: as no crew member could get to the pilot's aid in emergency, there was thus at least a long-odds chance that the gunner might achieve a non-calamitous landing. First delivered to the RAF in December 1940, these aircraft became operational with No. 85 Squadron on 7 April 1941. A second batch of about 100 DB-7As was converted similarly, but were each provided with 12 nose-mounted machine-guns, and were designated Havoc II. About 40 DB-7s were modified to serve as night intruders, retaining the bomb aimer's nose and able to accommodate up to 2,400 lbs (1089 kg) of bombs; an armament of four 7.7 mm (0.303 in) machine guns was mounted beneath the nose. Officially named Havoc I (Intruder), the type also acquired such unofficial names as Moonfighter, Ranger and Havoc IV. Whatever the name, the aircraft were operated with considerable success by No. 23 Squadron. In order to enhance the somewhat limited capability of the AI radar installed in the Havoc Is, 31 were each equipped with a Heilmore/GEC searchlight of some 2,700 million candlepower intensity. Known as Havoc II Turbinlites, the aircraft were used, with little success, to illuminate German aircraft after stalking to within contact distance, when escorting Hawker Hurricane fighters would be able to attack and destroy the well-lit target. The name Havoc was adopted subsequently by the USAAF as the general name for its A-20s of all versions.

A few DB-7As were retained for use in a light bomber role under the designation Boston III, but the UK had ordered an improved version, the DB-7B, with changed electric and hydraulic systems, and instrumentation which conformed to RAF requirements and layout. These also were designated Boston III, and carried four 7.7 mm (0.303 in) guns in the nose, another two on a high-speed mounting in the aft cockpit, and a seventh gun firing through a ventral tunnel, plus a bomb load of up 2,000 lb (907 kg). These Boston IIIs were used extensively by squadrons of No. 2 Group, incuding Nos. 88, 107, 226 and 342. They served also with Nos. 13,14,18,55 and 114 Squadrons in North Africa from early 1942, replacing Bristol Blenheims.

Initial USAAC contracts for the DB-7, placed in May 1939, produced 63 A-20s with turbocharged Wright R-2600-7 Cyclone 14 engines and of these three were converted to serve in a photo-reconnaissance role with the designation F-3. The remainder became the XP-70 prototype and 59 P-70 production night fighters, the prototype with unsupercharged R-2600-11 engines, and all with British-built AI radar and an armament of four Hispano 20 mm cannon mounted beneath the fuselage. These night fighters were used primarily in a training role, so that USAAC crews could become conversant with the newly developed technique of radar interception.

The first bomber version to serve with the USAAC was the A-20A, generally similar to the A-20, but powered by unsupercharged R-2600-3 engines and with armament as for the DB-7B except that the machine-guns were of 7.62 mm (0.30 in) calibre. In addition, two remotely-controlled aft-firing guns were mounted in the rear of each engine nacelle, and the bomb load was 1,100 lbs (499 kg). One XA-20B prototype was modified from a production A-20A, and had a changed armament. This was not adopted for production A-20Bs, which had two 12.7 mm (0.50 in) nose mounted guns, and which were in most respects similar to the DB-7A.

Large-scale production dictated more standardisation, so that the RAF's Boston 111 and USAAC A-20C were one and the same, equipped with R-2600-23 engines. To boost production, Douglas granted a licence to Boeing and this latter company produced 140 A-20Cs for supply to the RAF under Lend-Lease as Boston IIIAs: they differed in their electrical system, and in some changes to the ancillary equipment of the engines. DB-7s of this version were supplied also to the USSR under Lend-Lease during 1942.

The next major production variant was the A-20G, of which almost 3,000 were built by Douglas at Santa Monica. These also had R-2600-23 engines, and were some 8 in (0.20 m) longer to provide a nose armament comprising two 12.7 mm (0.50 in) machine guns and four 20 mm cannon, and either two 12.7 mm (0.50 in) guns or one 12.7 mm (0.50 in) and one 0.30-in (7.62-mm) gun in the rear cockpit. Most of the early production A-20Gs in this configuration were supplied to the USSR; the next A-20G variant had the 20-mm cannon replaced by 12.7 mm (0.50 in) machine guns; and the final variant introduced a rear fuselage 6 in (0.15 m) wider to accommodate an electrically-operated dorsal turret with two 12.7 mm (0.50 in) guns, underwing bomb racks to accept an additional 2,000 lbs (907 kg) of bombs, extra fuel tanks in the bomb bay, and provision for an underfuselage drop tank to provide a ferry range of more than 2,000 miles (3219 km). This was, of course, vital for the type's deployment in the Pacific theatre where their arrival in 1942 came as something of a mixed blessing to Major General George C. Kenney's 5th Air Force, struggling to defeat the Japanese threat to New Guinea. As delivered, the aircraft were considered to be too lightly armed, so the basic armament was supplemented by four 12.7 mm (0.50 in) machine guns, and as there were no bombs available as required for their employment in a close-support role, Kenney suggested the provision of 23 lbs (10 kg) fragmentation bombs with small parachutes attached. With the A-20s each able to carry 40 of these 'parafrag' bombs, the aircraft played a vital role in dislodging the enemy from Burma.

Other improvements introduced gradually to A-20G Havocs included improved armour, navigation equipment and bomb aiming controls, and winterisation accessories for aircraft to be operated in the low temperature zones. Also produced were 412 A-20Hs, with little change from the A-20Gs except for the installation of 1,700 hp (1268 kW) R-2600-29 engines. Neither the G nor H version served with the RAF, but the A-20J and A-20K, bomb leader versions of the A-20G and A-20H respectively, were built for both the USAAF and RAF, with the respective designations Boston IV and Boston V in service with the latter air force. They differed only by having a frameless transparent nose to enhance the bomb aimer's view.

When production ended, on 20 September 1944, Douglas had built 7,385 DB-7s of all versions, and these had been used by the USAAF and its Allies in the widest imaginable number of roles. They had been supplied also to Brazil, the Netherlands and the USSR, and small numbers from those received by the UK had been diverted to serve with the Royal Australian Air Force, Royal Canadian Air Force, Royal New Zealand Air Force and South African Air Force. In addition one A-20A had been supplied to the US Navy, under the designation BD-1, and used for evaluation. In 1942 eight A-20Bs were procured for use as target tugs under the designation BD-2.

Battle Honours and Operational History

The A-20 Havoc saw no operational action with the Fleet Air Arm in WWII. However, it served with distinction with other services in every theatre of the war. On 4 July, 1942, the first Army Air Forces bomber mission over Western Europe was flown by US crews of the 15th Bomb Squadron operating RAF Havocs against airfields in the Netherlands. Some of the Dutch aircraft were captured by the Japanese and appropriated into service.