From Defeat in the West, by Milton Shulman (Secker & Warburg, 1947; Dutton, 1948; Arcadia, 2017), Kindle Loc. 3695-3718:
About fifty divisions of the Wehrmacht had been committed to battle in Normandy — well over a million men. Fewer than ten of these divisions could still be classed as reasonable fighting formations after the Seine River had been crossed. Of a total of about 2200 tanks and assault guns used in Normandy, almost 1800 of them remained as burnt-out hulks in the rolling fields west of the Seine. About 210,000 Germans had become prisoners-of-war since the invasion, and another 240,000 had been either killed or wounded. In other words almost half of the total number of German troops engaged in the battle of Normandy had appeared on a Wehrmacht casualty list in one category or another.
The losses amongst senior commanders were commensurately as high as those suffered by the men. For in addition to the normal hazards of the battlefields, German generals were also subjected to the tantrums and intuitions of their Fuhrer. Hitler succeeded in dismissing his senior officers almost as quickly as the Allies managed to kill, wound or capture them. By 25 August three field marshals had been eliminated — von Rundstedt had been dismissed, von Kluge had taken poison and Rommel had been wounded. Amongst army commanders, Dollman of Seventh Army had died, his successor Hausser had been severely wounded in the Falaise Gap, Geyr von Schweppenburg of Panzer Group West had been recalled to Berlin, and von Salmuth of Fifteenth Army had been replaced by von Zangen. And farther down the military hierarchy no fewer than three corps commanders and twenty divisional commanders had been killed, captured or wounded. The battle of Normandy had cost the German Wehrmacht in three months almost twice as many men as they had lost at Stalingrad where 250,000 troops had surrendered to the Russians. And as additional satisfaction to Allied commanders, the Seine had been reached two weeks ahead of schedule and the broad strategical battle had been fought exactly as planned.
Retreat had been well learnt by the Wehrmacht in Russia. In fact, by the end of August 1944, it had almost become a habit. Once the German General Staff was given complete freedom to carry out a straight, administrative task it usually did it well. Having once decided to withdraw behind the Seine, the fact that no bridges existed over the river below Paris constituted a relatively minor problem. Crossing rivers while going backwards was a specialty of staff officers who had been chased back over the Volga, the Don and the Dnieper. With the destruction of the Seine bridges it had been necessary early in the campaign to organize a system of ferries and pontoons for the sending of supplies and reinforcements to Normandy. These well-camouflaged crossing places now did yeomen service in the reverse role of transporting the broken units to the comparative safety of the east bank. Harassed by a vigilant Allied air force, almost 300 barges were destroyed or damaged in the seven days preceding 23 August when the exodus was at its height. Although the west bank of the Seine was choked with abandoned vehicles, knocked-out guns and tanks, and frightened horses, thousands of German troops succeeded in crossing the Seine at Rouen, Elbeuf, Caudebec and Duclair.