Subsequently, French Cavalry were perceived between Mellet and Villers Perruin; whereupon Colonel Marwitz, who had been reinforced by two Squadrons of the Pomeranian Hussars, ordered a change of front of his Brigade in this direction, then deployed his eight Squadrons in two lines, with considerable intervals, and withdrew them, alternately, towards the high road; followed, though not vigorously, by three French Regiments of Cavalry and a Battery, comprising Jaquinot's Light Cavalry Brigade, attached to d'Erlon's Corps. As he approached the chaussée, the 2nd and 3rd Battalions of the 2nd Elbe Landwehr, as also the 3rd Battalion of the 22nd Regiment, advanced to his support.
Until about six o'clock the action along that part of the line which extended from Sombref to Balatre, had not been carried on with any degree of energy, and the occupation of the opposing forces was generally limited to mutual observation. Now, however, the French Infantry (of which only a small portion was attached to Grouchy's Cavalry), penetrated as far as the precincts of the Village of Tongrines; but Colonel Kämpfen's Brigade (the Tenth), having been successively reinforced by all the Battalions of Colonel Luck's Brigade (the Eleventh) excepting one which was left in reserve, the French were easily repulsed, and the Prussians maintained full possession of all this portion of their original position.
It was about seven o'clock when the Aide de Camp returned from his reconnaissance, and reported to Napoleon that the Column in the distance which had caused so much uneasiness proved to be d'Erlon's Corps; that Girard's Division, upon being undeceived, had resumed its position in the Line of Battle; and that Vandamme's Corps had maintained its ground.
This movement of d'Erlon's Corps admits of being satisfactorily explained. Napoleon, having received information that d'Erlon had been left in reserve in front of Gosselies, and inferring, perhaps, from this circumstance that Ney was sufficiently strong to be able to hold his ground at Quatre Bras, without further aid than what he had at hand, resolved upon employing this Corps upon the Prussian Right Flank; but in the meantime, d'Erlon had, in pursuance of instructions from Ney, continued his march towards Quatre Bras; and having himself proceeded in advance, had reached Frasne, at which place Colonel Laurent found him, and communicated to him the Emperor's Order for the march of his Corps upon St Amand; adding that on coming up with the head of his Column, he had taken upon himself to change its direction of march into that of St Amand. D'Erlon hastened to comply with Napoleon's wishes, and despatched General d'Elcambre, his Chief of the Staff, to make known the movement to Marshal Ney.
His route from Frasne towards St Amand, the point prescribed by the Order, lay through Villers Perruin, and the movement was altogether one of a retrograde nature. Hence the direction of the Column, as seen in the distance, was well calculated to alarm the troops of the French extreme Left; as also to excite surprise in the mind of Napoleon, who having formed no expectation of the arrival of any French troops in the Field by any other direction than that from Gosselies upon St Amand, or perhaps from Quatre Bras upon Bry, also participated in the opinion that the Column in question, under its attendant circumstances and general disposition, could be no other than that of an Enemy. As d'Erlon debouched from Villers Perruin, and advanced upon the prescribed point, St Amand, he threw out his Cavalry (Jaquinot's) to his Left, for the protection of this Flank; and it was before this Cavalry that the Prussian Brigade, under Colonel Marwitz, retired in the manner already explained, a movement which fully restored confidence to Girard's Division.
All at once this Column was observed to halt, to indicate an indecision in its intentions, and finally to withdraw from the Field. D'Erlon had in fact just received from Ney a peremptory Order to join him without delay, with which he resolved to comply, probably concluding that he was bound to do so from the circumstance of his having been in the first instance placed under the Marshal's immediate command; having ascertained also from the Emperor's Aide de Camp that he was not the bearer of any instructions whatever from Napoleon as to his future movements, and that the appearance of his Corps upon that part of the Field of Battle had been quite unexpected. This pressing Order had been despatched by Ney immediately previous to the arrival of Colonel Laurent on the Heights of Gemioncourt.
If the first appearance of this Column had caused alarm and perplexity among the troops of the French Left Wing, the apprehensions it excited on the Prussian Right, when its Cavalry was observed to advance and to drive back Colonel Marwitz' Brigade, which had been sent towards it en reconnaissance (as already explained), were still greater; and its equally unexpected disappearance (with the exception of its Cavalry, and a portion of its Infantry), at a moment when it was felt that its vigorous co-operation must have rendered the issue of the Battle no longer doubtful, was looked upon as a particularly fortunate turn of affairs; and Blücher's hopes revived as he prepared to carry into effect his meditated attack upon the French Left Flank.