The Nazi Smart Bombs

Thursday, March 13th, 2014

Precision-guided munitions seem extremely modern, but Nazi Germany developed many missile and precision-guided munition systems during World War II, including the Fritz X radio-controlled bomb and the Henschel Hs 293 radio-controlled guided missile — another glide-bomb, but with small wings and a rocket engine slung underneath it.

They failed as wonder weapons though, if only because the Germans had lost air superiority:

It’s hard to estimate losses caused by the guided weapons. German air raids saturated Allied defenses by combining smart bomb attacks with conventional dive bomber and torpedo assaults, so it is always not clear which weapon hit a ship.

The Allies also tried to maintain morale by attributing guided weapon losses to conventional weapons.

Bollinger counts 903 aircraft sorties that carried around 1,200 guided weapons. Of those 1,200, almost a third were never fired because the launch aircraft aborted or were intercepted.

Of the remaining 700 weapons, another third malfunctioned. Of the approximately 470 whose guidance systems worked, at most 51 — or just over 10 percent — actually hit their targets or landed close enough to damage them.

Bollinger calculates that just 17 to 24 ships were sunk and 14 to 21 damaged.

“At most, only one weapon in 24 dispatched from a German airfield scored a hit or damage-causing near miss,” Bollinger writes. “Only about one in 14 of the missiles launched achieved similar success, and at most one in nine of those known to respond to operator guidance was able to hit the target or cause significant damage via a near-miss.”

“This is very different from the 50-percent hit rate experienced during operational testing,” Bollinger points out.

To be fair, the technology was new. There were no lasers or fire control computers. The Fritz-X and Hs 293 were manually guided all the way. Operators had to track both missile and target through cloud, fog and smoke, without the benefit of modern thermal sights.

“It was virtually impossible to hit a ship that was steaming more than 20 knots and could fire back,” Bollinger tells War is Boring. “Almost all of the hits were against slow and/or defenseless targets.”

Bollinger hypothesizes that a phenomenon called “multi-path interference,” unknown at the time, may also have hampered the performance of the Hs 293. Radio command signals sent from the bomber to the missile might have overshot the weapon, bounced off the ocean surface below and interfered with the missile guidance signal.

The early jammers were ineffective, but Bollinger believes that by the time of the Normandy assault in June 1944, the equipment had improved enough to offer a measure of protection — and partly explains why German missiles performed poorly later in the war.

Strangely, while the Germans took measures to counteract Allied jamming of their air defense radars, they never really addressed the possibility that their anti-ship missiles were also being jammed.

It’s wrong to blame the bomb for the faults of the bomber. The real cause for the failure of German smart bombs was that by the time they were introduced in late 1943, the Luftwaffe was almost a spent force.

Already thinly spread supporting the hard-pressed armies in Russia and the West, the German air arm suffered relentless bombardment by U.S. B-17s and B-24s. The Third Reich could never deploy more than six bomber squadrons at a time equipped with the Fritz-X and Hs 293.

When the Luftwaffe ruled the skies over Poland and France in 1939, this might have been enough. By late 1943, a guided-bomb run was practically suicide.

German bombers making daylight attacks had to run a gauntlet of fighters protecting Allied ships in the daytime. Night attacks were marginally safer for the bombers but still exposed them to radar-equipped British and American night fighters. The Allies aggressively bombed any airfield suspected of harboring the smart bombers.

“Allied fighter air cover was by far the most important factor,” Bollinger tells War is Boring. “Not only did it lead to large numbers of glide-bombing aircraft getting shot down, it also forced the Germans to shift missions from daylight to dusk or nighttime. This in itself lead to a major and measurable reduction in accuracy.”

Many raids would cost the Germans a few bombers. By the standards of the thousand-bomber raids over Germany, this was trifling. But for the handful of specially trained and equipped Luftwaffe squadrons, it was catastrophic.

Of the 903 aircraft sorties, Bollinger estimates that in 112 of them, the bombers were lost before launching their weapons. Another 21 were shot down or crashed on the return flight, for an overall loss ratio of 15 percent.

“Each time a pilot departed on a glide bomb mission, he had almost a one-in-seven chance of never returning in that aircraft safely,” Bollinger says. “Put another way, the probability that a pilot would return safely after each of the first 10 missions was only 20 percent.”

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