existence was kept secret but—much to the annoyance of the Americans—its
wider deployment was delayed in the belief that as soon as it was used the
enemy would be able to adopt the technique both in radar and in counter
measures.
23 The delay however did not apply to airborne interception—these
aircraft were not expected to leave UK air-space and so any lost equipment
could be recovered.
23 But for ASV, a vital tool in detecting and attacking
surfaced U-boats charging their batteries at night when travelling to and from
their bases along the Bay of Biscay, the operational delay of about 9 months
23
cost the Allies an estimated 1.5–2 million tons of merchant shipping in the
North Atlantic.
23 The eventual failure of the U-boat campaign in May
1943
23 was undoubtedly due to the deployment of the magnetron along with
the work of the code-breakers at Bletchley Park.
23 The delay also affected
RAF Bomber Command—although they already had the electronic bombing
aids GEE and OBOE that extended their capabilities as far as the Ruhr—but
the eventual deployment of the magnetron in continental bombing raids via
the ‘H2S’ radar system—largely again at the insistence of the Americans—led
to a huge improvement in Allied bombing accuracy. ‘H2S’—a name probably
derived from the term ‘Home Sweet Home’—was the first ever ‘blind’ airborne, ground scanning radar system. It was designed to pinpoint targets for
night-time and all-weather bombing to improve the accuracy of RAF
bombing over Germany. Although air-crews invariably claimed their bombs
had dropped ‘on-target’, the photographic interpreters showed that fewer
than half the bombs dropped at night fell within five miles of their target;
photographic reconnaissance also revealed that only one in three of the
bombers reaching the vicinity of the target, bombed within 1 mile of it and of
the total sorties, the bombs were scattered over an area of 41 sq miles around
the assigned target.
23 H2S allowed an attacking aircraft to map the ground it
was flying over and find features such as towns, lakes and rivers. The images
were crude at first but improved steadily after its deployment in 1943. The
system was installed in relatively few ‘Pathfinder’ bombers such as the de
Havilland Mosquito. These used ‘H2S’ to accurately identify targets and
illuminate them with incendiary flares; for the main force of ‘follow-up’
bombers, targeting their objective was then—in comparison—‘a piece of
cake’ (Plate 17.3).
However, the crash of a British aircraft near Rotterdam in February 1943
allowed the Germans to recover the magnetron—its ‘self destruction’
mechanism having failed on impact. But the Germans were already well aware
of the technology, so that nothing had really been gained by delaying its
deployment operationally. However the German failure to employ the
technique themselves, their inability to understand the extent to which the
410
D. Sheppard
wider deployment was delayed in the belief that as soon as it was used the
enemy would be able to adopt the technique both in radar and in counter
measures.
23 The delay however did not apply to airborne interception—these
aircraft were not expected to leave UK air-space and so any lost equipment
could be recovered.
23 But for ASV, a vital tool in detecting and attacking
surfaced U-boats charging their batteries at night when travelling to and from
their bases along the Bay of Biscay, the operational delay of about 9 months
23
cost the Allies an estimated 1.5–2 million tons of merchant shipping in the
North Atlantic.
23 The eventual failure of the U-boat campaign in May
1943
23 was undoubtedly due to the deployment of the magnetron along with
the work of the code-breakers at Bletchley Park.
23 The delay also affected
RAF Bomber Command—although they already had the electronic bombing
aids GEE and OBOE that extended their capabilities as far as the Ruhr—but
the eventual deployment of the magnetron in continental bombing raids via
the ‘H2S’ radar system—largely again at the insistence of the Americans—led
to a huge improvement in Allied bombing accuracy. ‘H2S’—a name probably
derived from the term ‘Home Sweet Home’—was the first ever ‘blind’ airborne, ground scanning radar system. It was designed to pinpoint targets for
night-time and all-weather bombing to improve the accuracy of RAF
bombing over Germany. Although air-crews invariably claimed their bombs
had dropped ‘on-target’, the photographic interpreters showed that fewer
than half the bombs dropped at night fell within five miles of their target;
photographic reconnaissance also revealed that only one in three of the
bombers reaching the vicinity of the target, bombed within 1 mile of it and of
the total sorties, the bombs were scattered over an area of 41 sq miles around
the assigned target.
23 H2S allowed an attacking aircraft to map the ground it
was flying over and find features such as towns, lakes and rivers. The images
were crude at first but improved steadily after its deployment in 1943. The
system was installed in relatively few ‘Pathfinder’ bombers such as the de
Havilland Mosquito. These used ‘H2S’ to accurately identify targets and
illuminate them with incendiary flares; for the main force of ‘follow-up’
bombers, targeting their objective was then—in comparison—‘a piece of
cake’ (Plate 17.3).
However, the crash of a British aircraft near Rotterdam in February 1943
allowed the Germans to recover the magnetron—its ‘self destruction’
mechanism having failed on impact. But the Germans were already well aware
of the technology, so that nothing had really been gained by delaying its
deployment operationally. However the German failure to employ the
technique themselves, their inability to understand the extent to which the
410
D. Sheppard