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The Battle of the Ruhr: how the Flak 88 anti-aircraft gun played a pivotal role

The Battle of the Ruhr: how the Flak 88 anti-aircraft gun played a pivotal role

This month sees the release of a new Haynes Workshop Manual title -  ‘Flak 88’. In this feature, we take a look at this formidable anti-aircraft gun and also a major battle in which it played a prominent defensive role.       

A Formidable Weapon

The ‘Flak 88’ gun was a key component of German ground-based anti-aircraft defences in the Second World War. The word ‘Flak’ is derived from the term ‘Flugzeugabwehrkanone’ (aircraft defence canon), whilst ’88’ is a reference to the weapon’s 88mm calibre. 

The Flak 88 could fire high explosive shells to well over 25,000 feet, higher indeed than the service ceilings of contemporary British heavy bombers.

Although heavy, the Flak 88 was a very mobile artillery piece that was quick to deploy and had a rapid rate of fire. All in all it was a very potent weapon, and allied bomber crews were justifiably wary of it.

A direct hit from an ’88’ would more than likely destroy an aircraft outright, whilst the shrapnel from a nearby air burst could cause significant damage to the airframe or engines. Bombers had very thin outer surfaces, so the crews were vulnerable to the shrapnel too.              

Attacking the Ruhr

March 2018 also sees the 75th anniversary of the start of ‘The Battle of the Ruhr’, an allied strategic bombing offensive that lasted 5 months, targeting Germany’s industrial heartland.

The majority of the bombing sorties were carried out by Royal Air Force Bomber Command, flying at night. The Ruhr was heavily defended by Flak 88 batteries and other anti-aircraft guns, and by very capable Luftwaffe fighter aircraft.

Earlier in the war the smog of the Ruhr valley had hampered the RAF’s efforts to locate targets there, but by 1943 high-flying De Havilland Mosquito ‘Pathfinder’ aircraft were able to find targets for the main bomber force using an electronic navigation aid code-named Oboe.

The first RAF raid of the campaign, on March 5th, was directed at Essen but on that mission only about 35% of the bomber force succeeded in dropping their payloads within 5km of the target area even though it had been marked with the aid of Oboe. 

During the course of the campaign various cities including Cologne, Dortmund and Dusseldorf were also attacked, with mixed results.

Hunters and the hunted

The RAF bombers were pursued by heavily armed German night fighters. Most night fighters were directed to their targets by ground radar stations, although some utilised onboard ‘Lichtenstein’ radar sets instead.

Night raids were invariably deadly games of cat and mouse, the bomber crews desperately trying to spot approaching night fighters whilst also trying not to get caught in the sweeping searchlight beams or hit by flak from the batteries of 88s. 

Their aircraft would often be clearly silhouetted against the fires raging below, making it easier for night fighters to find them.

A sudden cessation of anti-aircraft fire could indicate the imminent arrival of night fighters. British bombers were defensively armed with lightweight rifle-calibre machine guns that were often out-ranged by the cannons and heavy machine guns of the attacking German aircraft.

If however there was sufficient warning from a fellow crew member, a bomber pilot could resort to drastic manoeuvres in an attempt to evade an approaching night fighter.

By this time in the war, RAF Bomber Command had switched to using the ‘Bomber Stream’ tactic whereby large numbers of bombers flew in long tight formations along a precisely defined route, making it harder for German ground controllers to identify individual targets for night fighters to attack, and for flak units to focus on individual targets passing overhead.

Although definitely more successful than the previous practice of sending bombers out individually (with each bomber plotting its own course to the target), the heavy concentration of night fighters and anti-aircraft guns meant that RAF losses were still high over the Ruhr. The Ruhr Valley was nicknamed (with typical British irony) ‘Happy Valley’ by the bomber crews. 

By the summer, almost a third of all Germany’s anti-aircraft guns were deployed in the Ruhr area, and well over 500 nightfighters. At the end of July, in light of the RAF’s mounting losses, the decision was taken to call-off the offensive. The campaign is however credited with severely disrupting German steel and aircraft production.

A Ruhr veteran

The RAF bomber force in the Battle of the Ruhr included the Avro Lancaster, the Handley Page Halifax, the Short Sterling and the Vickers Wellington. The Lancaster (serial number R5868) on permanent display at the RAF Museum in Hendon, North London, is a veteran of the Battle of the Ruhr.

It participated in raids on Essen, Dortmund, Dusseldorf, Cologne, Bochum, Krefeld and Wuppertal whilst operated by No. 83 squadron based at RAF Wyton in Cambridgeshire.

This particular aircraft went on to complete 139 missions during the war, a remarkable achievement considering that, on average, Lancasters survived only twenty-one missions.                 

Key facts about the Flak 88

  • A single Flak 88 anti-aircraft battery typically consisted of four guns, their firing co-ordinated by a centralised control system.
  • Generally, anti-aircraft shells had barometric fuses (set to specific altitudes) or time-delayed fuses.
  • Flak 88s were manufactured by Krupps. The last Essen raid of the Battle of the Ruhr (25/26 July 1943) caused severe damage to a Krupps factory there.
  • The Flak 88 was also used successfully in the anti-tank role.
  • ‘Operation Chastise’, the famous ‘Dam Busters’ raid of 16/17 May 1943, took place during the Ruhr campaign (although one of the targets, the Eder Dam, was not in the Ruhr Valley).
  • United States Army Air Force bombers flew some missions during the Battle of the Ruhr but by day, using tight defensive formations to concentrate their defensive fire against fighter attacks.

For more information on the aircraft mentioned in this article, check out these Haynes Owners manuals: Avro Lancaster, De Havilland Mosquito, Handley Page Halifax, Short Stirling, Vickers Wellington. For information on ‘Oboe’, see page 96 of the Royal Air Force 100 Technical Innovations Manual.