Let us now see what generally were the movements of the German and of the Allied forces between September 3 and September 6 when the Battle of the Marne began.
Leaving two army corps, the 2nd and the 4th Reserve corps, on the Ourcq to cover his flank and rear, General von Kluck struck south-east across the Marne with the 3rd, 4th, and 7th corps. The main body crossed the river at La Ferté-sous-Jouarre, and took the main route to Sezanne. Others crossed higher up between La Ferté-sous-Jouarre and Château-Thierry. For this purpose they threw bridges across the river. The Marne is deep and for 120 miles of its course navigable.
These movements were covered and screened by the 2nd division of cavalry, which advanced towards Coulommiers, and the 9th division, which pushed on to the west of Crecy. Both places are south of the Marne and east of Paris.
Writing of these events at the time, Mr. W. T. Massey, special correspondent of the Daily Telegraph, observed that:—
The beginning of the alteration of German plans was noticeable at Creil. Hidden by a thick screen of troops from the army in the field, but observed by aerial squadrons, the enemy were seen to be on the move. Ground won at Senlis was given up, and the German troops, which at that point were nearer Paris than any other men of the Kaiser's army, were marched to the rear. Only the commandants in the field can say whether the movement was expected, but it is the fact that immediately the enemy began their strategic movement British and French dispositions were changed.
The movement was expected. Indeed, as we have seen, the whole strategy of the campaign on the French side had been designed to bring it about.
The Germans must have observed that their new intentions had been noticed, but they steadily pursued their policy. Their right was withdrawn from before Beauvais, and that pretty cathedral town has now been relieved of the danger of Teuton invasion. The shuttered houses are safe, temporarily at any rate.
The ponderous machine did not turn at right angles with any rapidity. Its movements were slow, but they were not uncertain, and the change was made just where it was anticipated the driving wedge would meet with least resistance.
In the main the German right is a tired army. It is a great fighting force still. The advance has been rapid, and some big tasks have been accomplished. But the men have learnt many things which have surprised them. They thought they were invincible, that they could sweep away opposition like a tidal wave. Instead of a progress as easy as modern warfare would allow, their way has had to be fought step by step at a staggering sacrifice, and in place of an army which took the field full of confidence in the speedy ending of the war and taught that nothing could prevent a triumph for German arms, you have an army thoroughly disillusioned.
In this connection the service of the British Flying Corps proved invaluable. Covering though they did a vast area, and carefully as they were screened by ordinary military precautions, the movements of the Germans were watched and notified in detail. Upon this, as far as the dispositions of the Allied forces were concerned, everything depended, and no one knew that better than General Joffre. On September 9 he acknowledged it in a message to the British headquarters:—
Please express most particularly to Marshal French my thanks for services rendered on every day by the English Flying Corps. The precision, exactitude, and regularity of the news brought in by its members are evidence of their perfect organisation, and also of the perfect training of pilots and observers.
Farther east the army of General von Bülow (the 9th, 10th, 10th Reserve corps, and the Army corps of the Prussian Guard), advancing from Soissons through Château-Thierry, and crossing the Marne at that place as well as at points higher up towards Epernay, was following the main road to Montmirail on the Petit Morin.