The year 1943 was a turning point in the war. The military production of the United States, Britain, the Soviet Union, and Germany all increased significantly during the year, but the difference can be found when looking at the overall economic strength of each country.
Production capacity in the UK is now at a standstill, the US has deep potential to be tapped, and Germany is starting to decline. On the surface, the output of German workers was still growing until 1944, but its national economy had begun to decline since 1943, and such an imbalance was certainly not sustainable. After 1943, due to the strategic bombing of the US and British air forces, the German industrial structure was seriously unbalanced. A prime example of this is the fact that a cave factory can produce a large number of advanced jet fighters, but there is no fuel to fly them. Therefore, although the Allies and the Axis still won and lost each other on the battlefield, the outcome of the war had already been decided.
After the Casablanca Conference in January 1943, the United States and Britain launched a joint bombing offensive, and the specific bombing order was (1) the submarine industry, (2) the aviation industry, (3) the transportation system, (4) the oil industry, and (5) other military targets. When the US Air Force attacked the German aviation industry, the British Air Force still adhered to its pre-war operational thinking, directed the spearhead of the attack at the Ruhr industrial area, and launched the Ruhr campaign on 3 July, especially the attack on 3 German dams (Monet, Edair, Solpei).
The dam conundrum
Large German dams, which are usually made of poured concrete, are very solid targets, so they have to be bombed with super-heavy bombs. With World War II-era technology, each Lancaster heavy bomber could only carry one bomb large enough to destroy a large dam.
At that time, in order to avoid the threat of medium and small-caliber anti-aircraft guns, British heavy bombers mainly adopted the method of high-altitude horizontal bombing in dense formations at night. However, the accuracy of high-altitude horizontal bombing is very low, even if the new H2S navigation system is used for night bombing, only 50 bombs can fall within 8 km of the aiming point, and 10 bombs can fall within 3 km of the aiming point (calculated based on the experience of the British Air Force in attacking Ruhr cities in 1943). If you bomb an arsenal, the hit rate is only 2% or 3%. For a point target such as a dam, it is difficult to cause serious damage even with super-heavy bombs if it does not hit the dam body directly. So the method of high-altitude horizontal bombing was ruled out due to poor accuracy.
There is also a way to directly attack the dam from the upstream direction with an air-dropped torpedo, the accuracy of which is ***. The power of the torpedo warhead is equivalent to a 500-kilogram bomb, and the use of water pressure during underwater attacks can also increase the destructive power, and if you concentrate multiple torpedoes to attack a little, you can cause huge damage to the dam. However, Germany had been prepared for this, deploying anti-aircraft artillery around several dams and setting up multiple mine nets in the upstream direction. Therefore, the low-altitude torpedo attack was also rejected.
Bouncing bombs
After repeated analysis of the aerial photographs of the dam**, the British Air Force identified the weak point of the German defense: there were no large number of blocking balloons in the river near the dam, which left a gap for bombers to enter at ultra-low altitudes. Despite such a loophole, Britain still did not have a suitable bomb that could balance both power and accuracy.
Designer Barnes Wallis took inspiration from a game of water rafting for kids. If a super-heavy bomb can bounce forward on the water, it can go over underwater mine nets. As long as the bomb is dropped at the right distance, it can accurately hit the part of the dam that is above the water, and the bomb will be even more destructive when it sinks into the water near the dam.
After the pool test, it was proved that the spherical bomb model can bounce after obtaining a certain muzzle velocity. Later, the British Air Force used Mosquito and Wellington bombers to carry out a number of ultra-low-altitude dropping simulated bomb tests, and the final conclusion was that the barrel-shaped bomb was most suitable for bouncing bombing, but before dropping, a bomb hanging mechanism was required to give the bomb a 500 rotation per minute to the rear. In addition, the bomber needs to maintain a speed of 350 kilometers per hour and drop the bomb at about 18 meters (60 feet), at which point the bomb can bounce off the surface of the water without sinking underwater.
To carry 4300 kg of super-heavy bombs, the British Air Force specially modified the magazines of the Lancaster heavy bombers of the 617th squadron. The inside of the bomb compartment is equipped with a bomb hanging mechanism driven by an electric motor, which can drive the bomb to rotate before dropping the bomb, because the jumping bomb is too large, the bomb body can only be exposed outside the bomb bay, and each aircraft can only hang one bomb at the center of gravity of the aircraft.
In order to carry out this special mission, the pilots of the 617th Squadron chose similar terrain on the rivers in the United Kingdom and conducted long-term ultra-low-altitude flight training. The Lancaster heavy bomber itself is heavy and has a lot of inertia, which makes it unsuitable for ultra-low-altitude flight, especially when maneuvering in situations such as turning along rivers and avoiding obstacles. In order to maintain an accurate flight altitude at night, pilots came up with ingenious methods. Two searchlights shining on the lower right of the fuselage are installed, and when the two apertures coincide on the water, the height is exactly about 18 meters. In this way, through the joint efforts of scientific researchers and pilots, an almost whimsical bombing mission was finally ready, and only an order to attack and a bright moon night were needed.
In May 1943, the British Air Force often sent a squadron of more than a dozen bombers to paralyze the German air defense system in order to cover this attack. On one occasion, just 10 British planes inexplicably left 25 million Germans in bomb shelters. Reich Marshal Goering was furious with several of his subordinates over this.
Attack process
On May 16, 1943, it was a full moon night, and the 617th Squadron of the British Air Force dispatched 19 Lancaster heavy bombers, under the command of Squadron Leader Gibson, to load the bouncing bombs and begin"Punitive action"。The Lancaster formation flew as low altitude as possible when crossing the English Channel, strictly maintaining radio silence to avoid the German coastal radar network and the Luftwaffe's interception.
The attack aircraft group was divided into 3 formations: the 1st squad consisted of 9 aircraft, under the direct command of squadron leader Gibson. The mission is to storm Monet's Dam first, and then attack the Edair Dam after a successful attack. Squad 2 consisted of 5 aircraft and was specifically tasked with assaulting the Solpe Dam. The 3rd squad consisted of the remaining 5 aircraft and acted as a reserve to attack in place of the other squads if they did not complete their mission;If all targets have been destroyed, Team 3 attacks the other 3 dams that have been selected as reserve targets. The actual battle proved that this plan was too optimistic, and due to the large losses of the attack aircraft group, only 3 of the main targets were destroyed.
The AJ-H bomb fell off during the flight and had to return to base. AJ-K, AJ-B, AJ-C, AJ-S, AJ-E, AJ-W were shot down by the Germans over the Netherlands. Having penetrated inland, the bomber formation chose a tortuous course, first to the south, then from the north bypassing the Ruhr industrial area with dense air defense, and finally from the north to the north of the dam complex. Such a route made it impossible for the Germans to determine the final bombing target and avoid organized interception. Despite this, in the end, only 12 planes reached the target and attacked the Monet, Edair, and Solpe dams.
The 617th squadron commander Gibson's AJ-G aircraft were the first to attack the Monet dam. The bomber entered the combat course from the river upstream of the dam, and the bomb drop altitude was accurately controlled at about 18 meters. However, due to the distance of the bomb, the bomb was outside the effective destruction range after 3 jumps**. The AJ-M aircraft was damaged by anti-aircraft artillery during the second attack, which caused the bomb to be dropped too close, and the bomb jumped over and destroyed the generator building. The AJ-P aircraft then made a third attack, and the bomb blew a gap nearly 20 meters long at the top of the dam. The AJ-A aircraft hit the dam during the 4th attack, and the bomb was underwater**, dealing a fatal blow to the dam. The AJ-J in the back found that the dam had broken when it entered the combat course, and the fifth bomb accurately hit the gap in the dam, and the ** force widened the gap in the dam to more than 70 meters wide. At this point, the Monet Dam completely burst.
Only 3 Lancasters attacked the Edair Dam. The Edair Dam is located at a bend in the river, and the dam is not far upstream from the high river bank, and the bomber needs to dive and turn to enter the attack course, so it is difficult for the pilot to stabilize the aircraft at the ideal altitude while leaving enough distance for the bombardier to aim. The AJ-L repeatedly entered the attack without success. The AJ-Z dropped the bomb on the second entry, but the bomb was at the top of the dam**, so it did not cause structural damage. The AJ-N also dropped bombs on its second combat course. The bomb hits the dam after 3 jumps, blasting a large hole with a diameter of 10 meters in the dam**. The dam then burst under water pressure.
The formations attacking the Solpe dam did not encounter terrain difficulties, but visibility was not high. The AJ-T dropped its bomb only during the 10th attack, and the bomb hit the top of the dam, blowing a gap. AJ-F also blew a gap in the dam during its 6th pass. The Solpe Dam withstood two attacks and did not cause a levee breach.
Dam structures
Both Monet and Edair are arch dams. The dam body of the arch dam is convex to the upstream direction, adopts a thrust structure that bears axial pressure, the stress is evenly distributed, and part of the horizontal load is pushed to both banks, and the other part is transmitted to the dam foundation through the vertical beam. The stability of the dam body mainly depends on the support of both banks, not on its own weight. For construction, the advantage of arch dam is that the thickness of the dam body is small and the amount of work is small. The disadvantage is that the construction is difficult, and the geological and topographic conditions at the bottom of the riverbed and on both banks are high. When the arch dam is attacked by a bomb, once the surface stress structure of the dam body is damaged, the huge water pressure cannot be evenly dispersed, and it is likely to widen the gap and cause the embankment to burst.
Solpe is a concrete trapezoidal gravity dam. The gravity dam profile is triangular or trapezoidal, and the tensile stress caused by water pressure is offset by the compressive stress generated by the self-weight of the dam body. The gravity dam has a large amount of engineering, but the dam body is relatively strong, and the requirements for the geological conditions of the riverbed are not high. All three dams were accurately hit by super-heavy bombs at least twice (3 from Monet, 2 from Edair, and 2 from Solpei), and 2 of the arch dams were destroyed immediately, while the concrete gravity dam was only damaged at the top of the bomb and did not burst due to water pressure. It can be seen that the strength of concrete gravity dams is indeed better than that of arch dams.
Summary of actions
Two more bombers crashed on the way back to the attack formation, resulting in a bomber loss rate of up to 42 per cent (operations in which bomber losses of more than 10 are generally considered unsustainable). Fifty-six pilots died, more than many costly mass bombing campaigns. But it was still a successful bombing campaign throughout the Ruhr campaign. Because only 19 bombers were dispatched this time, the results of the battle can be compared with many 1,000-plane bombing operations.
More than 1,200 people died in the floods alone, and they also washed away roads, railways, bridges, towns, coal mines and factories within 160 kilometers downstream. Electricity from the three dams provides energy to the Ruhr industrial area and supplies water to the local irrigation system for farmland and inland waterway navigation. This attack cost Germany a significant amount of water resources. It was not until the autumn of that year that Germany was able to restore the damaged lines of communication and power generation capacity, and it took a lot of manpower and material resources.
An attack on a dam can have a combined destructive effect, which is valuable from a purely military point of view. However, article 56 of the Protocol to Supplement Article 1 of the Geneva Conventions provides:"Factories or facilities that contain potentially dangerous elements, i.e. dams, embankments and nuclear power plants, are attacked to unleash dangerous forces of nature that result in severe losses to civilians and cannot be attacked even if they become military objectives. "Therefore, if Britain had not held firm air supremacy at home, and the German bomber force had been in decline by this time, Britain would not have dared to make such a move under the threat of equal retaliation.
The experience of the European theater of World War II proved that the selection of energy systems as targets for strategic bombing was extremely effective. After the Allied command did not realize this until 1944, American and British strategic bombers concentrated on bombing Germany's synthetic fuel, coal, and power generation facilities, accelerating the defeat of Nazi Germany.
Thank you for reading.