The first dam to be attacked was the Mohne. Gibson flew over the dam once and then informed the other aircraft circling out of range of the flak that he was going to attack. As the aircraft passed over the spit of land, so low that the bomb-aimer told Gibson he was going to hit the trees, the navigator turned on the spotlights and gave Gibson instructions of “down…down” until the aircraft was at 60’, meanwhile the mine was spinning at 500 rpm and the bomb-aimer using the primitive but effective home-made sight waited for the right moment to release the bomb. The flak towers on the dam opened fire and the front-gunner of Gibson’s Lancaster fired back. Gibson admitted to being very frightened as his brightly lit aircraft became the target for every gun in the area but concentrated on keeping the aircraft lined up and rock steady at 60’ while his flight engineer adjusted the speed. At 28 minutes past midnight they dropped their Upkeep mine at 230 mph on a bearing of 330 degrees. It bounced three times, but sank short of the wall. After a short delay the hydrostatic pistols detonated the bomb at the correct depth and a great spout of water surged up and over the dam wall. At first it was thought the dam had collapsed, but as the water subsided it was seen still to be intact. After allowing the waters of the lake to settle, Gibson called Hopgood in to attack. The flak gunners now knew what to expect and the aircraft was seen to be hit several times on the approach. The bomb-aimer knew that their orders were to be sure to drop the mine correctly and was considering ordering another run when the aircraft was hit.
Hopgood ordered the mine to be released. This, unsurprisingly, resulted in the bomb being dropped late, and it bounced right over the dam and exploded, wrecking the main power house. Hopgood’s aircraft was on fire and he ordered the crew to bale out as the Lancaster struggled to 500’ and then exploded. Only the rear gunner and the bomb-aimer baled out successfully and both men had chosen to pull the ripcord of their parachutes inside the aircraft, which undoubtedly saved their lives – all the other crew members perished. Martin attacked next, with Gibson flying alongside him to distract the flak gunners, and the mine was dropped at 38 minutes past midnight on a bearing of 335 degrees at 217 mph. It veered to the left and exploded near the bank of the reservoir twenty yards from the dam.
Gibson now called up Young. Martin flew on Young’s left to distract the gunners while Gibson flew parallel to the dam on the downstream side hoping to divide the fire from the defences on and beyond the dam. Young made the perfect approach and drop, and his bomb hit the centre of the dam. The dam was apparently intact after the attack, and Maltby was making his bomb run with Martin and Gibson both acting as decoys when he saw the centre of the dam crumbling. Maltby veered to one side and dropped his mine which bounced, struck the dam and exploded. The dam was already failing before Maltby’s mine exploded, and now millions of gallons of water were pouring through the breach and down the valley and beyond. Gibson, who had already ordered Shannon to prepare to attack, cancelled the order and instructed Shannon, Maudslay, and Knight to accompany him to the Eder dam, along with Young, who was to act as deputy leader if anything happened to Gibson.
We overflew the Dam on the headings of Gibson's aircraft, flying parallel and across the face of the downstream side. The clearance on either side of the dam is approximately half a mile and at 230 mph would take a significant angle of attack to clear the obstacles. This was no easy task to achieve.