Outbreak of war lined up at
RAF Tengah,
Singapore, In September 1939, the month in which the Second World War broke out, the Blenheim Mk.I equipped two home-based squadrons and 11 overseas squadrons in locations such as
Egypt,
Aden,
Iraq,
India, and
Singapore. Further RAF squadrons had received, or were in the process of converting to, the more capable Blenheim Mk.IV and 168 Blenheim Mk.IV aircraft had entered RAF operational strength by the outbreak of war. The raid was a failure, only nine aircraft attacked, and only superficial damage was done to the
cruiser Emden, when one of
No. 107 Squadron's Blenheims crashed into the cruiser, killing 11 crewmen.
RAF Coastal Command were soon using the Blenheim to protect British shipping convoys off the east coast. Several squadrons of Blenheim IVs were assigned to the AASF, being frequently used against targets in France and the
Low Countries once the Battle of France had begun. Blenheims were also assigned to the air component of the
British Expeditionary Force of the
Army. German attacks upon the French airfields also damaged a considerable number of Blenheims on the ground. On 14 May, a combined force of
Fairey Battles and Blenheims was dispatched on a counter-attack on German forces breaking through defensive lines but 40 out of 71 aircraft were lost in this sortie. This is the worst losses proportionally taken by the RAF. Around 50 Blenheims supported the
Dunkirk evacuation by harassing enemy forces. Rapid advances in technology in the late 1930s rendered the Blenheim obsolescent by 1939. In particular, it had become heavier as extra service equipment was installed that was found to be necessary through operational experience. This, coupled with the rapid performance increases of the fighters that would oppose it, had eclipsed the Blenheim's speed advantage. In January 1941, the
Air Staff classified the Blenheim as inadequate in terms of performance and armament for current operations.
Home front Blenheim squadrons were still in demand after their withdrawal from France as part of the British action during the
Norwegian campaign. Typically operating from bases in northern Britain, such as
RAF Lossiemouth, flying for extended periods over the
North Sea led to the weather posing almost as much of a risk as enemy combatants, particularly as most of the Blenheim IVs lacked heating or
deicing systems and in response, some aircraft were fitted with boilers on the starboard engine exhaust. Heavy losses occurred, caused by both enemy action and engine failures due to
icing. Blenheim units operated throughout the
Battle of Britain, often taking heavy casualties, although they were never accorded the publicity of the fighter squadrons. From July to December 1940, Blenheims raided German-occupied airfields both in daylight and at night. Although most of these raids were unproductive, there were some successes; on 1 August five out of twelve Blenheims sent to attack
Haamstede and Evere (Brussels) were able to bomb, damaging (50 per cent, 40 per cent and 10 per cent) three Bf 109Es of II./JG 27 at Leuwarden and apparently killing a
Staffelkapitän identified as
Hauptmann Albrecht von Ankum-Frank. Two other 109s were claimed by Blenheim gunners. Another successful raid on Haamstede was made by a single Blenheim on 7 August which destroyed one 109 of 4./JG 54, heavily damaged another, and caused lighter damage to four more. There were also some missions which produced an almost 100% casualty rate amongst the Blenheims. One such operation was mounted on 13 August 1940 against a
Luftwaffe airfield near
Aalborg in north-western
Denmark by twelve aircraft of
82 Squadron. One Blenheim returned early (the pilot was later charged but was killed on another operation before a
court martial was held) while the other eleven, which reached Denmark, were shot down, five by flak and six by Bf 109s. Blenheim units had also been formed to carry out long-range strategic reconnaissance missions over Germany and German-occupied territories. In this role, the Blenheims once again proved to be too slow and vulnerable against
Luftwaffe fighters and they took constant casualties. On 12 August 1941, an action described by
The Daily Telegraph in 2006 as being the "RAF's most audacious and dangerous low-level bombing raid, a large-scale attack against power stations near Cologne" took place. The raid was a low-level daylight raid by 54 Blenheims under the command of Wing Commander Nichol of
114 Squadron. They hit their targets (Fortuna Power Station in
Oberaußem-Fortuna and the Goldenberg Power Station in
Hürth-Knapsack), but twelve of the Blenheims were lost during the raid, 22% of those that took part, which was far above the sustainable loss rate of less than 5%. The England cricketer
Squadron leader Bill Edrich was awarded the
DFC for his part in the raid. From 5 September 1940 Blenheims of Bomber Command began a bombing campaign targeting German-occupied ports along the
English Channel, alongside heavier bomber types. Bomber Command Blenheims also performed anti-shipping patrols due to Coastal Command's own strike squadrons being heavily depleted throughout the latter half of 1940. On 11 March 1940, a Blenheim IV,
P4852, became the first RAF aircraft to sink a
U-boat, having scored two direct hits on in the
Schillig Roads. In April 1941, a campaign aiming to completely close off the Channel to enemy shipping was launched using an initial flight of Blenheims stationed at
RAF Manston. Between April and June that year, a total of 297 Blenheims of
No 2. Group attacked German shipping at sea, losing 36 aircraft, while Coastal Command launched 143 attacks in the same period, losing 52 aircraft; by the end of the year, 698 ships had been attacked and 41 of these sunk for the loss of 123 aircraft. Upon the outbreak of the
Pacific War in December 1941, some Blenheim squadrons in the Middle East were relocated from the theatre to the Far East in response to the new threat from Japanese forces.
South East Asia flying low to attack a Japanese
coaster off
Akyab,
Burma on 11 October 1942 Blenheims continued to operate widely in many combat roles until about 1943, equipping RAF squadrons in the UK and at British bases in
Aden, India,
British Malaya, Singapore, and the
Dutch East Indies. Many Blenheims were lost to
Japanese fighters during the
Malayan Campaign and the battles for
Singapore and
Sumatra. One Blenheim pilot, Squadron Leader
Arthur Scarf, was posthumously awarded the
Victoria Cross for an attack on
Singora,
Thailand, on 9 December 1941. Another bomber of
No. 60 Squadron RAF was credited with shooting down Lt Col
Tateo Katō's
Nakajima Ki-43 fighter and badly damaging two others in a single engagement on 22 May 1942, over the
Bay of Bengal. Katō's death was a severe blow to the
Imperial Japanese Army Air Force. The Air Ministry's replacement for the Blenheim as a medium day bomber, another Bristol design, the
Buckingham, was overtaken by events and changes in requirements, and considered inferior to the
de Havilland Mosquito, and as such did not see combat. The final ground-attack version – the Blenheim Mk.V – first equipped 139 Squadron in June 1942. Eventually thirteen squadrons – mainly in the Middle East and Far East – received this variant but generally operated them only for a few months. One Blenheim Mk.IV left in Java by the retreating British forces in 1942 ended up in the hands of the fledgling
Indonesian Air Force (AURI). They repaired it, installed
Nakajima Sakae engines, painted it in their colours, and flew it around
Yogyakarta on at least three occasions.
First attack on the Japanese carrier force On 9 April 1942, nine Blenheims from
11 Squadron attacked the
1st Air Fleet (
Kidō Butai); the
Imperial Japanese main
carrier battle group (Admiral
Chūichi Nagumo). The Blenheims approached undetected by the
A6M2 Zero combat air patrol (CAP) fighters and surprised the Japanese carrier battle group. While the bombers attacked fleet carrier from an altitude of , they missed. This was the first time a Japanese carrier force had faced a concerted air attack in the
Pacific War. The Finnish Blenheims flew 423 missions during the Winter War, and close to 3,000 missions during the
Continuation War and
Lapland War. Blenheim machine-gunners also shot down eight Soviet aircraft. Thirty-seven Blenheims were lost in combat during the wars. After the war, Finland was prohibited from flying bomber aircraft by the
Paris Peace Treaty, with Finland's Blenheims being placed into storage in 1948. However, in 1951, five Blenheims were re-activated for use as
target tugs, with the last flight of a Finnish Blenheim taking place on 20 May 1958. The usual nickname of Blenheim in the Finnish Air Force was
Pelti-Heikki ("Tin Henry"). ==Variants==