The Bristol Blenheim entered Bomber Command service in 1937, with No. 114 squadron, and soon became one of the command’s most important aircraft. By the time of the Munich crisis in 1938, sixteen home based squadrons (Of Nos.1, 2 and 5 Groups) were equipped with the Blenheim Mk I. By the outbreak of war in September 1939, the Mk I had been largely phased out of Bomber Command, equipping only two squadrons, in favour of the Mk IV. This version equipped six squadrons of No. 2 Group, as well as one pool squadron, two army co-operation squadrons and one night fighter squadron.
The Blenheim Mk IV achieved a number of early firsts for Bomber Command. A Blenheim of No. 139 was the first British aircraft to enter German airspace, carrying out a reconnaissance over the German naval base at Wilhelmshaven on 3 September 1939. Flight Officer A. McPherson found his target, but the aircraft’s radio froze at high altitude preventing him making a report.
The next day the Blenheim Mk IV became the first British aircraft to attack a target in Germany. Fifteen Mk IVs from Nos. 107, 110 and 139 squadrons were sent to attack German warships in the Schillig Roads, near Wilhelmshaven. Of the fifteen, only ten from Nos. 107 and 110 Squadrons found their targets, and of those ten aircraft, five were lost. The only serious damage inflicted by the raid came when one Blenheim crashed into the cruiser Emden. The light bombs in use proved to be entirely useless against the armoured decks of the German warships.
The Blenheim suffered heavily during the Battle of France. Loses in the air were matched by heavy losses on the ground. No. 144 squadron lost almost its entire strength of Blenheims to a bombing attack. After two days of fighting an initial force of 135 Fairey Battles and Blenheims had been reduced to 71 aircraft. Reinforcements kept coming, but the losses kept mounting. The attacks on the Sedan bridgehead on 14 May that famously saw the loss of so many Battles, also saw five out of eight Blenheims lost. Another seven were lost in another attack on the bridgehead later that day. The majority of Blenheims sent to France were lost either to the fighting, or destroyed to prevent them falling into German hands.
The fighting in France revealed the Blenheim Mk IV to be under armoured, under armed and too slow. The problem was that any attempt to solve the first two problems would simply make the third one worse.
Blenheim IVs of Bomber Command were heavily involved in operation Channel Stop, an attempt to prevent German coastal convoys from travelling at day. The Blenheim was involved in this duty from April 1941 until October 1941, when it was replaced by more modern aircraft, including the Boston and Ventura bombers, imported from America. Once again losses had been heavy, this time in the face of both heavily armed flak ships and German fighter patrols.
The Blenheim played a minor role in the early strategic bombing campaign. They took part in the raid on Mannheim of 13 December 1940 that began to reveal how inaccurate British night bombing actually was at this time. They were also involved in a number of costly daylight raids against German targets.
During 1941 the RAF began a series of offensive operations over German occupied France, code named Circus. The aim of these operations was to force Luftwaffe fighters to react, allowing the British fighters to engage and destroy them. Early operations without a bomber component had been ignored by the Germans. With the Blenheims attacking ground targets, the Germans were more often forced to respond, but they were now operating over home territory. The Circus operations were a costly failure – the RAF lost twice as many aircraft as the Luftwaffe. However, after the German invasion of Russia in June 1941, it was essential that Britain was seen to be doing something to help, and so the raids continued throughout 1941.
The Blenheim was withdrawn from Bomber Command in August 1942, after a long period of decline. It was replaced by the Douglas Boston and Lockheed Vega Ventura as a light bomber.
Coastal Command did not receive the Blenheim until after the outbreak of war. In October 1939 four trade protection squadrons were formed. Another four transferred from Fighter Command in 1940. A Blenheim of No. 82 Squadron was the first British aircraft to sink a U-boat, sinking U.31 on 11 March 1940 in the Schillig Roads.
Four Coastal Command squadrons were eventually equipped with the Blenheim Mk IVF (Nos. 235, 236, 248 and 254), along with two R.C.A.F squadrons. No. 254, based at St. Eval in Cornwall, concentrated on anti-submarine warfare, but the remaining squadrons carried out a wide range of duties, including acting guard over downed Allied aircrews while rescue craft arrived, escorting shipping and attacks on German maritime patrol aircraft, which the Mk IVF was actually capable of catching and shooting down.
The Blenheim was phased out by Coastal Command in early 1942, in favour of newer aircraft, including the Beaufighter and the Mosquito.
The Blenheim Mk I was deployed to the Middle East even before the Mk IV began to replace it in Britain. No. 30 Squadron, based at Habbaniya, Iraq, was the first to receive the Blenheim, getting its first aircraft on 13 January 1938. When Italy declared war in 1940, the RAF had nine Blenheim squadrons in the Middle East – five in Egypt, three in Aden and one in Iraq. The squadrons based in Aden faced a much larger Italian force based in East Africa, while the Egyptian squadrons had to face west towards Italian North Africa.
Blenheims made the first British air attack on Italian positions in North Africa. At dawn after the Italian declaration of war on 10 June 1940 twenty six Blenheims from No.s 45, 55 and 113 squadrons attacked the Italian airbase at El Adem, destroying or damaging 18 Italian aircraft. The Blenheim played an important role in the early successful period in the desert in 1940 and early 1941, as the only modern RAF bomber in the theatre. It was only when the Luftwaffe began to appear in force that the Blenheim would find itself outclassed once again.
1941 saw five Blenheim squadrons sent to Greece, where they suffered very heavy losses during the German invasion. After the evacuation from Greece, No. 30 Squadron was sent to Crete, where it was virtually wiped out.
Blenheims were amongst the aircraft based on Malta in 1941. From their bases on that island they were able to inflict crucial losses on Rommel’s supply convoys, but once again at heavy cost. When the tempo of Axis attacks on Malta increased in early 1942, the Blenheim squadrons were forced to withdraw to Egypt, leaving Malta on 22 February 1942.
The Blenheim Mk IV remained active in the desert until the end of 1941. At that point most of the remaining Blenheim squadrons were rushed to the Far East, in a vain attempt to halt the Japanese onrush. By the time it left the desert, the Blenheim was hopelessly outclassed by the Bf 109. They would soon prove to be just as outclassed against the Zero.
That was not entirely the end of the Blenheim in North Africa. The Mk V saw service with four squadrons from November 1942, as part of the allied force involved in Operation Torch. This was a costly mistake – the Mk V was the slowest model yet. If it was caught by the Bf 109s, it suffered very heavily. Only two squadrons retained the Blenheim Mk V until the end of the desert war in May 1943
One of the more successful theatres for the Blenheim was East Africa. Three squadrons took part in the fighting there between June 1940 and the Italian surrender in May 1941 (although one did convert to the Martin Maryland during that period). Away from the Bf 109, the Blenheim had a better chance of survival and played an important role in repelling the initial Italian attack and then in the successful British counterattack.
The Blenheim Mk I reached India early in 1939. By the time of Pearl Harbor, three squadrons were equipped with the aircraft (Nos. 34, 60 and 62). On 8 December all three were in Malaya, but they could do little to stop the Japanese onslaught. Most of their aircraft were destroyed on the ground at their airbases in northern Malaya. Another squadron, No. 27, was sent to Singapore, where it suffered very heavy losses in early 1942.
More Blenheim squadrons were sent from the Middle East. Nos. 84 and 211 squadrons, with Blenheim Mk IVs were posted to Sumatra, arriving on 28 January. Once again they suffered heavy losses and on 18 February were forced to retreat to Java, where the survivors of No. 211 Squadron were absorbed into No. 84. On 1 March their airbase was attacked by Japanese tanks, and the remaining aircraft destroyed.
The three Blenheim squadrons involved in the long retreat through Burma were slightly luckier, as they were eventually able to retreat to relative safety in India, although by that time they were effectively out of aircraft.
Four squadrons of No. 211 Group later used the Blenheim MK V to attack Japanese positions in Burma from bases in India. By the Autumn of 1943 these aircraft had been replaced by more modern types.
The adoption of the Mk IV by Bomber Command meant that many Mk Is were now surplus to requirement. One use that was found for these aircraft was to convert them into long range escort fighters. This was done by fitting a gun pod, carrying four .303in machine guns, under the bomb bay. Seven squadrons had received the Mk IF by the outbreak of war.
Early combat experience proved the Blenheim to be entirely unsuited to the day time fighter role. However, it did have the internal space to carry the new airborne interception (AI) radar. One wing of Blenheims had been testing this equipment when the war broke out. A small number of radar equipped Mk IFs, of the Fighter Interception Unit, operated as night fighters through 1940 and into 1941.
It was a Blenheim Mk IF of the FIU that made the first successful interception using airborne radar, shooting down a Dornier Do 17 on the night of 21/22 July 1940. However, the Blenheim was too slow to make a truly successful night fighter – some of the German bombers were actually faster, and long stern chases were common. The Blenheim was phased on in favour of the Bristol Beaufighter, a much faster aircraft.
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