The deadly doodlebug

Germany's V-1 vengeance weapon

On June 13, 1944, exactly one week after Allied troops landed in Normandy, the Nazi war machine launched a vengeful strike against British civilians. Winged objects that looked like small airplanes and emitted a peculiar buzzing sound appeared over London. The buzz would cut out and the object would dive towards the ground, its 1,870 lb warhead exploding to kill men and demolish houses. The first strange bomb to fall struck near a railway bridge and killed six (some sources claim eight) civilians.

The weapon was the V-1 flying bomb, "V" standing for Vergeltungswaffe ("Vengeance Weapon" in English), a name that belied its function. It was originally intended to use a radio control system and strike military targets with high precision, but it quickly found its true use as a cheaply and quickly mass-produced terror weapon fired indiscriminately at cities, mainly London. It used a pulsejet engine, which creates thrust by rapid but discrete explosions, giving it its distinctive sound and its Allied nickname, buzz bomb. Its other English nickname, doodlebug, and the German equivalent Maikäfer ("maybug" in English), also refer to its buzz.

The weapon was developed at Peenemünde Army Research Center, a center for Nazi missile and rocket development. Compared to how much of a novelty it was, the V-1 was actually rather simple to build. The fuselage was sheet steel and the wings plywood. The control system comprised of two gyroscopes, a magnetic compass, a barometer and two cans of compressed air. Flight distance was controlled by an anemometer, a spinning weather vane-like device in the nose. It was driven to spin by air resistance, and the engine cut out once a predetermined number of spins (and a corresponding travel distance) was achieved.  The first patent for a pulsejet engine, one using steam power, was submitted by Nikolaj Afanasievich Teleshov, a Russian artillery officer, in 1867, just two years after the end of the American Civil War. The V-1 was simple enough to be assembled by slave labor – about 60,000 prisoners worked on Germany's V-weapons, 20,000 of whom died due to the horrible circumstances. The heart of the flying bomb, the pulsejet, was actually a surprising old idea.

V-1s were launched from a launch ramp called the Walter catapult, which used high-pressure steam to propel the bombs into the air. Once airborne, they were already flying fast enough so that air-flow entering the engine allowed the pulsejet to operate. Beside a small number of larger launch sites, 80 small, simplified and hard-to-discover sites were also built in Northern France, between Calais and Normandy. These sites could be built in two weeks, and when the time use them came, the Walter catapults could be erected in 7-8 days. A site could theoretically launch 15 V-1s a day, but actual performance often lagged behind this paper figure.

The Allies were scrambling for a solution against this new weapon. Its speed of 400 mph and cruising altitude of 2,000 to 3,000 ft made it a difficult target. It was flying so low and so fast that anti-aircraft guns couldn't turn fast enough to track it, and its altitude put it beyond the range of smaller guns but below the optimal range of heavier flak cannons. These deficiencies were eventually solved by faster-turning turrets, gun-laying (fire control) radar, and the introduction of the proximity fuze, which allowed flak shells to automatically detonate when they got close enough to a target. These changes eventually reduced the average number of shells needed to bring down one V-1 from 2,500 to 100.

In addition to flak batteries, likely approaches to London were protected by barrage balloons, balloons tethered to the ground by metal cables, which incoming flying bombs would hopefully hit. The Germans countered this particular defense by putting cable cutters on the leading edge of the V-1s' wings so they could simply cut their way through.

Aerial interception was another important defensive tactic. Only a few aircraft were fast enough to keep up with a V-1: the Hawker Tempest, which was only available in very limited numbers, and the de Havilland Mosquito, also known as the Wooden Wonder. The P-47M Thunderbolt could also do the job with a modified engine, and the P-51 Mustang and the Spitfire Mk XIV could be tuned to make them just about fast enough. The Gloster Meteor, one of the first jet planes, was also used to hunt V-1s, but had very unreliable cannons.
 
Stopping a V-1 by shooting at it was far from safe, since the intercepting plane was at a danger of flying straight into the resulting explosion. A difficult but safer way of getting the job done was by "toppling" the flying bomb. The interceptor would fly alongside the weapon, slip its wingtip under the buzz bomb's wing, and use it to nudge the thing upside down. This would disrupt the guidance system and cause the bomb to drop out of the sky. The number of such spectacular interceptions is somewhat debated, but some sixteen might have occurred.

Yet another defensive weapon was misinformation. All German spies in Britain have been turned into double agents in the so-called Double-Cross System, and these spies were used to send false information back to Germany about the effectiveness of the V-1. When the Germans (falsely) learned that most bombs overshot London, they shortened their flight times – causing them to actually fall short of the city's most densely populated central area.
 
Efforts to defend against V-1s (and, shortly after, V-2s and V-3s) operated under the umbrella term Operation Crossbow, which was also a preliminary step to the Normandy landings. The Allies already knew about the existence of German long-range secret weapons since May 1934, and took steps against them. While Crossbow integrated all the defensive measures, it also went on the offense with the strategic bombing of German production and launch sites. The effort was considered so important that in April 1944, Eisenhower declared that Crossbow has priority over all other strategic considerations, except the urgent needs of Operation Overlord. Possibly the best-known Crossbow operation was the last flight of Lt. Joseph P. Kennedy Jr., the brother of future U.S. President John F. Kennedy. Kennedy's mission was to take off in a B-24 Liberator crammed full of explosives, arm the explosives in the air, turn on a special remote control system and bail from the plane along with his co-pilot. Once the Liberator was no longer manned, another bomber would take control of it via a radio controller, fly it to France and deliberately crash it into an underground V-weapon facility. We don't know what went wrong, but the explosives detonated shortly after being armed, killing Kennedy and Lt. Wilford John Willy before they could have bailed.

The ultimate way to stop the V-1, however, was to exploit its greatest weakness: limited range. With a range of 160 miles / 257 km, the bombs could only reach London if they were launched from Northern France. By September 1944, the Allied troops liberating Europe have managed to overrun the launch sites, easing up the constant V-1 threat against London.
 
The threat was not completely gone, though. The Germans have attached V-1s to Heinkel He 111 bombers which could carry them part of the way, effectively extending the weapon's range. The bombers used a "lo-hi-lo" tactic: they approached Britain flying just above sea level to avoid radar, quickly climbed to a higher altitude, launched the flying bomb, then dove back down for the journey home. This, however, did not work very well. The failure rate of air-launched V-1s was very high, and the ignition of the pulsejet engine was bright enough to attract the attention of nearby Allied night fighters during night missions.

The Germans experimented with additional modifications to the V-1, but none of these panned out. Launching them from Arado Ar 234 jet bombers remained nothing more than a plan. Removing the warhead and using the bomb's fuselage as a towed external fuel tank for Messerschmitt Me 262 jet fighters was tried but discarded as too unstable. Even a piloted, semi-kamikaze V-1 was developed under the designation Fieseler Fi 103R, which would have allowed a pilot to steer the bomb to its target then hopefully bail out at the last moment. This vehicle, however, never saw action. Other attempts to increase the V-1's range, such as building them out of wood to make them lighter, or increasing the fuel tank's size at the expense of the warhead, also failed to achieve significant results.

With the frontline being pushed back toward Germany and London falling out of reach, V-1s were turned against targets in Belgium, most notably the port of Antwerp. The Germans hoped that by damaging the port sufficiently, they could prevent the Allies from shipping in supplies. The final V-1 launch site was only overrun by the Allies on March 29, 1945.
 
While the V-1s failed to do significant military damage or break the British will to fight, they did cause a great deal of suffering. Some 10,500 of them were fired against England. 5,500 people were killed and 16,000 injured in London, and a million other men were evacuated to the safety of the countryside. What most people don't realize is that more V-1s, 11,988, were launched against Antwerp than against London, but their poor accuracy and effective Allied defenses only allowed 211 buzz bombs to hit the port.
 
The V-2 was not the only vengeance weapon Germany unleashed on the Allies. The V-2 rocket followed shortly in its step, first launched in anger in September 1944. The destructive power of the V-2 was only slightly greater than the V-1's, and its range of 200 miles / 321 km wasn't that significantly better, either; its true advantage was its cruise altitude of 55 miles / 88 km, which put it far outside the range of any sort of flak or interception effort in existence at the time. In fact, vertically launched V-2s could fly even higher, and one of them became the first artificial object to pass the so-called “Kármán line”, the official boundary of outer space 62 miles / 100 km above sea level, in June 1944, before the missiles were ever used in the war. A third vengeance weapon also existed, but the V-3 was a large cannon instead of a rocket or missile.

The V-1's legacy was more impressive than its actual performance. Both the United States and the Soviet Union have captured V-1s (the latter from a test site in Poland) and shipped them home for research. The V-1 lived on in its American copy, the JB-2 Loon, also known as the Thunderbug, an important milestone in the development of modern cruise missiles.
 
Several V-1s survive to this day, usually in museums. You can see some of them at the Antwerp International Airport in Belgium, at the Deutsches Museum in Munich, or in the Netherlands, and a number of them in various locations in Great Britain, the Imperial War Museums in London and Duxford, for instance. You can also find several in the United States, perhaps most importantly at the National Air and Space Museum on the National Mall in Washington, D.C.