Reynaud stating that the Germans had broken through at Sedan, that the French were unable to resist the combination of tanks and dive-bombing, and asking for ten more squadrons of fighters to re-establish the line. Other messages received by the Chiefs of Staff gave similar information, and added that both Generals Gamelin and Georges took a serious view of the situation and that General Gamelin was surprised at the rapidity of the enemy’s advance. In fact, Kleist’s Group, with its immense mass of armour, heavy and light, had completely scattered or destroyed the French troops on their immediate front, and could now move forward at a pace never before known in war. At almost all points where the armies had come in contact, the weight and fury of the German attack was overpowering. They crossed the Meuse in the Dinant sector with two more armoured divisions. To the north the fighting on the front of the French First Army had been most severe. The First and Second British Corps were still in position from Wavre to Louvain, where our Third Division, under General Montgomery, had had sharp fighting. Farther north the Belgians were retiring to the Antwerp defences. The French Seventh Army on the seaward flank was recoiling even quicker than it had advanced.

From the moment of the invasion we began “Operation Royal Marine,” the launching of the fluvial mines into the Rhine, and in the first week of the battle nearly 1700 were “streamed.” 3 They produced immediate results. Practically all river traffic between Karlsruhe and Mainz was suspended, and extensive damage was done to the Karlsruhe barrage and a number of pontoon bridges. The success of this device was, however, lost in the deluge of disaster.

All the British air squadrons fought continuously, their principal effort being against the pontoon bridges in the Sedan area. Several of these were destroyed and others damaged in desperate and devoted attacks. The losses in the low-level attacks on the bridges from the German anti-aircraft artillery were cruel. In one case, of six aircraft only one returned from the successful task. On this day alone we lost a total of sixty-seven machines, and being engaged principally with the enemy’s anti-aircraft forces, accounted for only fifty-three German aircraft. That night there remained in France of the Royal Air Force only 206 serviceable aircraft out of 474.

This detailed information came only gradually to hand. But it was already clear that the continuance of fighting on this scale would soon completely consume the British Air Force in spite of its individual ascendancy. The hard question of how much we could send from Britain without leaving ourselves defenceless and thus losing the power to continue the war pressed itself henceforward upon us. Our own natural promptings and many weighty military arguments lent force to the incessant, vehement French appeals. On the other hand, there was a limit, and that limit if transgressed would cost us our life.

At this time all these issues were discussed by the whole War Cabinet, which met several times a day. Air Chief Marshal Dowding, at the head of our metropolitan fighter command, had declared to me that with twenty-five squadrons of fighters he could defend the island against the whole might of the German Air Force, but that with less he would be overpowered. This would have entailed not only the destruction of all our airfields and our air power, but of the aircraft factories on which our whole future hung. My colleagues and I were resolved to run all risks for the sake of the battle up to that limit – and those risks were very great – but not to go beyond it, no matter what the consequences might be.

About half-past seven on the morning of the 15th I was woken up with the news that M. Reynaud was on the telephone at my bedside. He spoke in English, and evidently under stress. “We have been defeated.” As I did not immediately respond he said again, “We are beaten; we have lost the battle.” I said, “Surely it can’t have happened so soon?” But he replied, “The front is broken near Sedan; they are pouring through in great numbers with tanks and armoured cars” – or words to that effect. I then said, “All experience shows that the offensive will come to an end after a while. I remember the 21st of March, 1918. After five or six days they have to halt for supplies, and the opportunity for counterattack is presented. I learned all this at the time from the lips of Marshal Foch himself.” Certainly, this was what we had always seen in the past and what we ought to have seen now.