By 2.00pm the majority of the German 13th Reserve Division was in position along the Chemin des Dames northeast of Braye, the adjutant of 3/RIR 53, whose battalion formed part of 27 Reserve Brigade, found himself approaching Cerny with, ‘11th Company as advanced guard and Machine Gun Company, main body of 10th Company, 2 batteries of Field Artillery Regiment, 9th and 12th Companies’. That afternoon 25 Landwehr Brigade – which according to General Maximilian von Poseck,39 the 2nd Cavalry Division had ‘picked up retiring from the direction of Bourg’ – joined them along with 1,200 reinforcements which had been intended for the Second Army’s X Corps in addition to a horse artillery Abteilung from the 9th Cavalry Division.⁴⁰ Thus by the afternoon of 13 September the crisis on the Aisne was practically over for the German Army. Moreover, on the same day Belgian operations emanating from Antwerp had come to an end with the Belgian Field Army retiring into and taking cover behind the city’s defences which in effect released Berthold von Deimling’s XV and Max von Boehm’s IX Reserve Corps for immediate duty on the Aisne.

RFC reconnaissance flights on 13 September were again hampered by poor weather but Captain Shephard and Lieutenant Kenlis Atkinson from 4 Squadron based at Saponay, northwest of Fère-en-Tardenois, managed to get airborne despite the, ‘tremendous gale and low cloud’, with the intention of observing the fighting east of Soissons, but it was to be a short flight as the wind proved to be to strong for the flimsy BE2, forcing them down near Orme. There was more success later when Atkinson was again observing with George Raleigh and this time they were airborne for ‘a little over an hour and saw the whole German position, no emplacements yet dug, so they are just getting into it’. Unfortunately whilst over Cerny, Raleigh accidentally switched the engine off, forcing them to glide down and land at Revillon where they found a brigade of French infantry which, much to their relief, ‘did not fire … but were very nice to us’. What Raleigh and Atkinson had probably seen was the vanguard units of the German VII Reserve Corps arriving and preparing positions on the Chemin des Dames; not only had the gap been closed but it had also been strengthened by relatively fresh troops which had not taken part in the retreat from the Marne.

The question inevitably arises; how close did the British and French come to exploiting the gap and establishing themselves firmly on the Chemin des Dames? The Official History tells us that there was a difference of some two hours between the first units of VII Reserve Corps arriving and the initial contact with British cavalry patrols. This may very well be the case but as I Corps was in no position to advance at the time it is of little consequence. Despite the reconnaissance report from 4 Squadron, which presumably reached GHQ at Fère-en-Tardenois sometime on 13 September, it was obviously still not clear to Sir John French that German troop movements from the north had in fact reinforced von der Marwitz. A further indication of substantial German troop movements had been observed on 12 September by two pilots from 2 Squadron who were forced to land behind enemy lines in a small field near Anizy-le-Château after their machine developed a fault. Incredibly Lieutenants Leonard Dawes and Wilfred Freeman landed their damaged aircraft between two large German columns which were on the roads either side of them and hid until nightfall in a nearby wood. Evading capture they navigated across country and swam the river eventually returning to their unit on 14 September, by which time the intelligence they had to report was of little use. If – as was probable – they had observed fresh units moving towards the Aisne and successfully reported their information it may well have encouraged I Corps to press forward with more haste on 13 September.

However, British intelligence on 13 September, devoid of the 2 Squadron report, suggested that the gap had not been substantially reinforced and there was little in front of I Corps but a strong force of cavalry and five batteries entrenched on the Chemin des Dames. Up until lunchtime this estimate was essentially correct, which together with the news that the French 35th Division had crossed the Aisne at Pontavert and that Conneau’s cavalry were already pressing the enemy at the eastern end of the Chemin des Dames, made the possibility of a break-through a realistic prospect to Douglas Haig at I Corps HQ.

It was not to be. By 1.00pm on 13 September the advance guard of Haig’s I Corps – 2 Infantry Brigade – had reached the top of the spur north of Bourg enabling patrols from C Squadron, 15/Hussars, to press on beyond Moulins and Vendresse and to reconnoitre towards the Chemin des Dames. Major Frederick Pilkington soon reported contact with the enemy in the form of, ‘large numbers north of Vendresse with artillery in position’. Later that afternoon another RFC reconnaissance flight sighted German columns moving towards Bourg from the direction of Chivy and, potentially more worrying for GHQ, the concentration of yet more enemy forces north of Courtecon. This time there could be no doubt that a fresh army corps was moving towards the Aisne and that substantial troop movements were taking place along the Chemin des Dames. Major Archibald ‘Sally’ Home was at Troyon on 13 September with 2 Cavalry Brigade and recalled seeing ‘masses of German cavalry moving all along the skyline on the main Rheims-Soissons road, we watched them for about two or three hours and estimated them to be a strong division’. He does not put a time on these observations but they may very well have been units of the 2nd and 9th German Cavalry Divisions.

The war diary of I Corps on 14 September indicates that the I Corps divisional commanders were aware that RIR 56 and RIR 53 were in position in the ‘Cerny-Troyon neighbourhood’ together with two Landwehr regiments, but it would not be for some days before the complete picture of German forces opposing them on the Chemin des Dames became apparent.41 What was not clear to the British at the time was the extent to which German units were being trawled from elsewhere and diverted towards the Aisne in order to bolster the forces already engaged along the Chemin des Dames. Consequently it was the arrival of fresh German units such as the mixed detachment from von Kirchbach’s XII Saxon Reserve Corps, 50 Brigade from the Fourth Army’s XVIII Corps and the five battalions from von Deimling’s XV Corps which would finally put an end to any hopes of a breakthrough.

The strength of German forces facing Smith-Dorrien’s II Corps was never in doubt. Von Lochow’s III Corps consisting of the 5th and 6th Infantry Divisions and 34 Brigade from IX Corps with two field artillery brigades were firmly in position by last light on 13 September; whilst in front of the British 4th Division the 3rd and 4th Infantry Divisions of von Linsingen’s II Corps, supported by 3 and 4 Artillery Brigades, were digging in above Bucy-le-Long. Overall this was still a formidable fighting force and despite the attrition of the previous weeks there were at least 100 – albeit under strength – German infantry battalions opposing the seventy-two tired and weakened infantry battalions of the BEF, a figure which would only be increased to eighty-four with the arrival of the 6th Division on 19 September.

Von Bülow was now nominally back in charge on the German side and this time he was clearly on the offensive. His orders for 14 September were for a general attack to consolidate the line of his three armies with the end result of pushing the Allied armies back over the Aisne. Even so, there was still doubt at OHL as to the successful outcome of the decision to stand and fight on the Aisne heights. Von Bülow entered the fray on 14 September with the OHL directive still on his desk: ‘If the First Army cannot hold the Aisne valley, it should retire in good time in the general direction of La Fère, behind the river valley’.