The daring special air attack on German dams, using bouncing bombs

9 minutes read.

The Dambusters were an elite group of Royal Air Force bomber crews, selected for a unique mission, with a unique weapon, in order to "have a chance to hit the enemy harder, and more destructively, than any small force has ever done before!".

The problem with strategic bombing

Barnes Wallis was an innovative British aircraft designer, especially bombers. Wallis knew, even before World War 2 started (and years before Bomber Command acknowledged the fact), that contemporary bombers and their standard 'small' bombs were not just terribly inaccurate, but also unable to destroy massive fortified targets, the truly strategic infrastructure targets which are essential to a country's continued ability to wage war.

He focused his attention particularly on the large water dams of the Ruhr valley, Germany's main steel production area, and steel is essential for military production. The dams provided electric power, and vast amounts of water, essential for steel production and for the transportation waterways which served it.

His original idea, used later in the war, was to produce huge 10 ton bombs with strong steel casing, to be dropped from very high altitude so that they would reach the ground at supersonic speed, penetrate many meters into the ground, and explode there. Even if they near-missed the target, the massive underground exlosions would instantly create large caverns and send shockwaves to the foundations of the target structure, causing it to collapse as if hit by earthquake. Wallis called it "Earthquake bomb".

How to destroy a huge dam

But the great German dams were too massive even for that. Wallis made experiments which proved that even a near miss wasn't enough, and that the only way to destroy the great dams was to explode large bombs at the base of the dam, in the water, and touching the dam wall, so that the explosion shockwave, combined with the water pressure, would directly hit the dam wall, and breach it. Torpedoes could not be used because the dams were protected from them with massive nets in the water, so it had to be an air-dropped bomb.

With 21st century precision-guided bombs, it's much easier, but in 1943, it was impractical, until Wallis came up with the idea of bouncing a massive bomb on the dam's lake surface, like a child bouncing a pebble on water, so that the bomb would bounce over the torpedo nets, hit the dam wall and sink there into the water, and only then explode, triggered by a water pressure fuze, not by impact.

This meant that a heavy bomber, flying very low and fast over the dam's water lake, at night (or it would be shot down for sure by the German defenders), at precisely the right altitude, at precisely the right speed, and drop the bomb at precisely the right distance from the dam wall, could do it. That seemed almost as impractical, but while the laws of physics could not be bent, elite bomber crews could perhaps be especially trained to do just that, at night, and under enemy fire.

Bomber squadron 617

Arthur Harris, the commander of RAF Bomber Command, selected Wing Commander Guy Gibson, a bomber and night fighter pilot who already flew 170 combat missions, to command the new elite squadron, and let him select the crews for it. Gibson was then 24 years old. The new squadron, formed on 21 March 1943, had less than two months for its special low flight training, becuase the attack on the dams was planned for mid May, when the water level, and water pressure on the dam, were highest.

The squadron's pilots quickly realized that they cannot achieve the required precise altitude and distance without proper means of measurement, but that was solved by equipping the bombers with precisely mounted downward spotlights, set so that their light beams would meet, forming an eight-shape, when the bomber would be at precisely the right altitude of 20 meters, and by a simple triangular aiming device of precise size, in which when held in front of the bombardier's eye, the two distant vertices would match the two towers on the dam wall when at the right distance for dropping the bomb.

The raid on the dams

On the night of 16 May 1943, nineteen Lancaster heavy bombers of squadron 617, each carrying a 9250 lb cylindrical bouncing bomb, took off, in three formations:
  1. Nine bombers, led by Gibson, would attack the largest dam, the Mohne, and if any bombs were left, would then attack the Eder dam.
  2. Five bombers would attack the Sorpe dam.
  3. Five bombers would take off two hours later, as reserve, and would either attack any of the three dams, or other smaller dams, as instructed.

The heavily loaded bombers flew very low all the way, along carefully planned routes, in order to minimize the risk of being hit by known anti-aircraft gun positions, or intercepted by night fighters, but once over the target, they could only attack a dam one bomber at a time, with delays between each, to let the water calm after each bomb's explosion. That gave the German anti-aircraft gunners, positioned on top of and near the dams, the opportunity to concentrate their fire at each incoming bomber while it was flying low and level over the dam's lake, heading right at them, and right in front of them.

Seven bombers did not make it to the dams. One bomber was lost from Gibson's formation on the way to the target. From the 2nd formation of five bombers, one was shot down by anti aircraft guns, one hit electricity pylons and crashed, one was hit by anti aircraft fire and lost both intercomm and radio, and therefore had to turn back, and one flew so low that its bomb hit the sea water and was torn off, so it had to turn back. So from the 2nd formation, a single bomber flew on, alone, to attack the Sorpe dam. And from the 3rd formation, the reserve, two bombers were lost on their way to the dams. The very low flying was essential, but so costly.

Valour in the face of the enemy

Eight bombers of Gibson's formation reached the Mohne dam, and Gibson made the first bomb run, with the others waiting safely away for their turn. Gibson's bomber flew over the big lake towards the huge Mohne dam, straight fast and low, and visible to the ten German anti aircraft guns which concentrated their fire at it. Gibson's turret gunners fired their machine guns back at the enemy gunners. Gibson's bomber kept flying in that hailstorm of tracer rounds fired at it and fired from it, dropped its enormous bouncing bomb at the correct distance from the dam, and streaked on, over and past the dam. The bomb bounced on the lake, reached the dam, sank in the water, and then exploded, raising water spray 300 meters high. When the water calmed, they saw that the huge dam was still standing, and two and a half minutes later, the 2nd bomber made its bomb run. It was hit by the anti aircraft guns, caught fire, released its heavy bomb past the dam, and then exploded and crashed.

Charging forward in the face of the enemy, which does its best to kill you, requires great courage. Doing it again, and then again, requires the highest valour, as Gibson did next. After the 2nd bomber was shot down, Gibson ordered the 3rd crew to attack, and told them that he will fly his bomber over the dam again, in order to attract the enemy gunners fire at him instead of at them. Gibson's support helped. The anti aircraft gunners fired at him first, and noticed the lower attacking bomber too late. The bomber was hit, but kept flying. Its bomb hit the dam, which kept standing. The two bombers then supported the 4th bomber's bomb run, flying over it from both sides, firing at the enemy anti aircraft guns and attracting their fire at them. The huge dam was hit again, and still held.

When the 5th bomber made its bomb run, the two bombers flew over its two sides and this time also lit their navigation lights, to further mislead the enemy gunners and attract their fire from the attacking bomber. The huge dam was hit again, the 4th time, and then it was breached, massively, and well over 100 million tons of water started to massively flood the Mohne valley past the breached dam.

Gibson ordered two of the 'empty' bombers to fly home, and led the remaining five bombers, with three remaining bombs, to their second target, the Eder dam.

Nighttime aerobatics, in very heavy bombers

The Eder dam was not protected at all by anti aircraft guns. The Germans believed that the topography around it, of high hill ridges, made it impossible to attack at night. It was almost so. It was as if they were trying to land their heavy bombers on an airstrip within a deep, short canyon, too deep and too short. The 1st bomber tried six times to dive towards the Eder lake, but kept failing to reach the precise combination of altitude, speed, and distance, which was essential for the bouncing bomb, and after each attempt it could barely climb out over the hills with its heavy load. The 2nd bomber made three attempts to bomb the Eder dam. On their 3rd attempt they dropped the bomb, but were apparently too fast, because the bomb exploded as it hit the dam, and the bomber was hit by the explosion as it flew over. The bomber flew on a few more seconds, and then crashed. The 1st bomber then returned for a 7th and then 8th bomb run attempt, in which it finally achieved the necessary combination, dropped its bomb, and then barely came out of the canyon in a steep climb. The dam kept standing. The last bomb was dropped by the last bomber on its third bomb run attempt, and it breached the Eder dam, causing over 200 million tons of water to flood the valley below.

The single bomber which remained from the 2nd formation reached the Sorpe dam alone, faced similar topographic difficulties as in the Eder, and also increasing fog. After nearly crashing, it successfully dropped its bomb at the 4th attempt, but the Sorpe dam remained standing.

The reserve formation was then ordered by radio to fly to the Sorpe and attack it. Two bombers were lost on the way to the target. One bomber reached the Sorpe dam, which was already covered with fog, and at their 10th attempt, after setting the nearby forest ablaze, and still unable to see the dam itself, they made a successful bomb run and hit the Sorpe, which remained standing. Another reserve bomber then reached the Sorpe dam, but then the entire valley was covered with fog, so it flew back home. The last reserve bomber attacked a smaller dam, also in fog, and at its 3rd attempt was able to make a successful bomb run, and hit the dam, which remained standing.

One of the bombers returning from attacking the Eder was hit by anti aircraft fire over the Dutch coast and crashed to the sea.

Of the 19 heavy bombers which took off for the Dambusters raid, 8 were lost, a terrible loss rate. 53 crew members were killed, and 3 survived and became prisoners of war. The heroic courage, determination, flying skill, and sacrifice, of these brave airmen of RAF squadron 617, are almost beyond words. The Dambusters raid was a great success. Two huge dams were breached, causing tremendous damages to the Nazi war effort, both immediate and longer term damages.

After the Dambusters raid

After the raid, Gibson was removed from operations and was sent to the USA. He later returned to operations and was killed on his way back from a mission. Squadron 617 suffered heavy losses in another strategic night attack, leaving just six of its original bomber crews still alive.

After that, it was decided that the squadron would continue so serve as a specialized elite squadron for performing strategic attacks with very large bombs, but no longer in the extremely dangerous low flying attack profile. Squadron 617 then used Barnes Wallis' new "earthquake bombs", mainly the 12,000 lb "Tallboy" bomb, and in the last weeks of World War 2 they received, and used, the 22,000 lb "Grand Slam" bomb. The squadron used the most advanced bombing sights for these huge bombs, and also developed its own special target finding and marking method, which required great courage and skill from the pilot of the target marking aircraft, who was typically the squadron's commander. In that role, dropping the heaviest bombs with the highest accuracy, squadron 617 destroyed many German strategic targets until the end of the war, including V-1 and V-2 missile sites, massively fortified submarine pens, massive strategic bridges, rail tunnels, underground facilities, and the battleships Tirpitz and Lutzow.

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World War 2 Bombers (7 minutes read)

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