Nightfighting in World War Two
By Lee Brimmicombe-Wood Part 5-1. Into the Bomber Stream THE STORY SO FAR: Josef Kammhuber, the head of the German nightfighters, perfects his Himmelbett system, a line of ground-controlled night-fighting zones that stretches from France to Denmark.
The night bombing campaign differed greatly from the day bombing effort. By day bombers clung together in tight formations, all the better to provide mutual gun protection. But by night, formation flying was near impossible, and dangerous too.
Until 1942 RAF's Bomber Command had been sending bombers over Germany in piecemeal fashion. The desire to limit accidents meant that bombers took off at well-spaced intervals. The crews would often choose their own routes to the target and lacking more than rudimentary navigation tools they would wander across the sky trying (and often failing) to find city-sized targets.
This all suited the Dunaja
systems perfectly. Lines of Freya-AN controlled fighting areas and Himmelbett
boxes stretched hundreds of miles across the Western approaches to Germany. Each area contained one nightfighter with a dedicated ground controller using radar plots to direct the pilot (see Part 4). The diffuse Bomber Command raids, spread over time and across airspace, would try to penetrate the line at multiple points. At each Himmelbett Raum
there would invariably be a nightfighter lying in wait for a bomber. The fighter often had the leisure to complete an interception--a process that could take ten minutes or so--before the next bomber would appear. As a result RAF losses were running at an unacceptable rate of almost 7%. ILLUSTRATION: This map shows the German nightfighter defences in early 1942. The coastal chain of dark fighting Freya-AN Dunaja zones is backed by a line of Himmelbett boxes ranging from Denmark into France. Each Freya and Himmelbett station could control only one fighter at a time. By mid-1942 the searchlights had been withdrawn to the cities, creating large illuminated zones (here marked in a lighter green) where Konaja, and later Wilde Sau, fighting could take place.
The arrival of Air Marshal Sir Arthur Harris--the infamous 'Bomber' Harris--marked a fundamental change in RAF tactics. The RAF radio monitoring service had identified the principles behind German controlled nightfighting and from this information Harris concluded that the answer was to concentrate bombers against a narrow section of the line in the shortest period of time. This would overwhelm the defence and produce tolerable levels of loss.
The first such operations took place in March and April 1942, when the RAF struck Lübeck and Rostock and suffered loss rates under 5%. The German leadership, instead of strengthening the night defences, chose to launch the retaliatory 'Baedecker Raids', and so Himmelbett
was again unprepared to meet Harris's unprecedented 'thousand bomber' raid on Köln on the night of 30/31 May 1942. A total of 1,047 bombers were concentrated into a raid of 90 minutes duration. It penetrated the Himmelbett
line on a front about 18 miles wide. No more than 8 night fighting zones were touched in the entire raid and just 25 Luftwaffe
nightfighters were guided to the enemy. Hundreds of pilots and radio operators sat helpless in cockpits and command posts while the RAF obliterated Köln's city centre at the rate of one bomb load every six seconds. Harris felt the loss rate, just 3.9%, well-justified.
Though Harris would only launch a handful of the thousand bomber raids, the tactics set the pattern for the remainder of the war. Bombers would set off at close intervals and form into a narrow gaggle, a 'bomber stream' some 150-200 miles long, that would swarm into Germany. Navigation was helped by the arrival of new radio aids, and though accidental collisions between bombers were not unknown, they were rare enough for Harris to be unconcerned about them.
Kammhuber responded by extending Himmelbett
down to the Swiss border, but he resisted calls from his pilots for 'free' fighting techniques against the streams. Kammhuber feared that a change of tactics would reduce his force's effectiveness and the control facilities needed for such operations were simply not available. In the meantime he demanded a massive expansion of the night fighting force. Göring thought the requests for new men and equipment utopian and flatly refused them. However, this didn't stop Kammhuber inducting personnel from the Nazi Party, SS, SA, Reich Youth Organization and Reich Labour Service as signals auxiliaries, bringing thousands of women into the night fighting force.
However, Kammhuber's star was falling and like Cassandra his warnings were increasingly ignored. When America entered the war he stated his belief that the USAAF would join the RAF on the night raids and called for further expansion of the night arm. Though his omens of American involvement were incorrect he was right to highlight the under-investment in night fighting. Göring was looking elsewhere for quick fixes to counter the night raids and appointed Major Hajo Hermann to head up a new unit of single-seat nightfighters. Hermann's suggestion was to exploit the withdrawal of searchlights from the Kammhuber Line (see Part 4). Reasoning that the skies over the city targets were now thick with searchlights, single-seat night fighters could fight without ground control or radar as the bombers made their approach. Best of all, Hermann reasoned, no expansion of the night force was necessary, because day fighters could be used.
Hermann's fighters were dubbed Wilde Sau
('Wild Boar') a German phrase akin to 'bull at a gate', because the scheme seemed so recklessly mad. They were blooded in July 1943 when the RAF launched a series of devastating raids against Hamburg, supported by a new jamming technique codenamed Window (to be described in Part 6). The jamming threw the radar defences into confusion and during the first night RAF casualties were just 1.5%. One of the emergency responses to the first raid was to throw Hermann's Wild Boars into the fight and initially they were quite successful. But over time the weaknesses of Wild Boar became apparent. Because it was reliant on searchlights it only worked over the target and could not weaken the enemy during the approach. The accident rate for single-seat fighters was greater at night unless they had special navigation aids and instrumentation. Another problem was co-operation with Flak; attempts to impose 'safe altitudes' for Flak to fire at failed and many Wild Boars were peppered by their own side. The fighters were borrowed from day units and would come back so shot up by Flak splinters that they were unflyable. The day pilots complained bitterly about the treatment of their aircraft and units began to refuse to assign machines to the Wild Boars. ILLUSTRATION: In this painting a Fw190A-7 Wilde Sau shoots down a Halifax above a cloudy sky on the night of a full moon. Some dramatic license has been taken by the artist. Where skies were clear, searchlights would light up the bombers for the Wilde Sau. On cloudy nights the searchlights would illuminate the clouds from below, and flak would shoot flares to light them from above. Illuminated this way, the clouds would become a shroud against which bombers could more easily be seen by fighters. However, combats under the full moon, as in the painting, became increasingly rare. Early in the war the bombers required the full moon, a 'bomber's moon', to navigate effectively. But as soon as the RAF adopted radio aids for navigation, they would avoid flying in full moon periods because they were vulnerable to freelancing day fighters like the Wilde Sau.