Vandeleur's and Vivian's Brigades constituted the Left Column, which was to effect its retreat by a Bridge over the Genappe at Thuy, still lower down the stream than that by which Alten's Infantry Division had crossed.
The Right Column was formed of part of the Third Light Cavalry Brigade, commanded by Major General Sir William Dörnberg, the 1st and 2nd Light Dragoons of the King's German Legion (under Lieutenant Colonels Bülow and de Jonquières), while the remaining Regiment, which was the 23rd British Light Dragoons (under Colonel the Earl of Portarlington), was employed as a portion of the Rear Guard of the Centre Column. The 15th British Hussars (under Lieutenant Colonel Dalrymple), belonging to the Fifth Cavalry Brigade, under Major General Sir Colquhoun Grant, was also attached to the Right Column; while of the two remaining Regiments of the Brigade, the 2nd Hussars of the King's German Legion (under Lieutenant Colonel Linsingen), and the 7th British Hussars (under Colonel Sir Edward Kerrison), the former had been left in occupation of a line of Posts on the French frontier, extending from Courtrai, through Menin, Ypres, Loo, and Fürnes, to the North Sea, and the latter formed a part of the Rear Guard of the Centre Column. This Right Column was to pass the Genappe by a ford higher up the stream than the town of Genappe.
These skilful dispositions had scarcely been arranged, when the Picquet of the 18th Hussars, on the left, came in at a good round trot, followed by two or three Squadrons of French Cavalry, upon which Vivian's Battery of Horse Artillery, opened a fire whereby their advance was checked. The Enemy, however, was observed to be very active in bringing up his Artillery, which soon opened upon the Hussar Brigade. Vivian, having received the Earl of Uxbridge's instructions to retire, accompanied with an intimation that he would be supported by Vandeleur's Brigade, then in his rear, and observing that the French Cavalry was pressing forward in great numbers, not only in his front, but also on his flank, he put his Brigade about, and retired in line, covered by the Skirmishers. The French followed, with loud cries of "Vive l'Empereur!" and just as the Brigade reached a sort of hollow, their guns again opened, throwing shells, which mostly flew over the heads of the 18th Hussars, against which Regiment they appeared to be principally directed. In the mean time, Vandeleur's Brigade had been drawn up in support, on rather a commanding position, and Vivian approached it in the full expectation that it would open out for the passing through of his own men, and take the Rear Guard in its turn; but on the Hussars arriving within fifty or sixty yards of the Fourth Brigade, Vandeleur put it about, and retired—Vivian not being aware that Vandeleur had previously received Orders to retire and leave the road clear for the retreat of the Cavalry in his front. Vivian immediately occupied the ground thus vacated, and, with a view to check the Enemy's advance more effectually, ordered the 18th Hussars to charge, as soon as the French approached within favourable reach.
The weather, during the morning, had become oppressively hot; it was now a dead calm; not a leaf was stirring; and the atmosphere was close to an intolerable degree; while a dark, heavy, dense cloud impended over the combatants. The 18th Hussars were fully prepared, and awaited but the command to charge, when the Brigade guns on the right commenced firing, for the purpose of previously disturbing and breaking the order of the Enemy's advance. The concussion seemed instantly to rebound through the still atmosphere, and communicate, as an electric spark, with the heavily charged mass above. A most awfully loud thunder clap burst forth, immediately succeeded by a rain which has never, probably, been exceeded in violence even within the tropics. In a very few minutes the ground became perfectly saturated; so much so that it was quite impracticable for any rapid movement of the Cavalry. The Enemy's Lancers, opposed to the Sixth British Brigade, began to relax in their advance, and to limit it to skirmishing; but they seemed more intent upon endeavouring to envelope, and intercept the retreat of, the Hussars. Vivian now replaced the 18th Hussars by the 1st Hussars of the King's German Legion, as Rear Guard, with Orders to cover well the Left Flank and Left Front of the Brigade. He had already sent off his Battery of Horse Artillery, to cross the Genappe by the Bridge of Thuy, and despatched an Aide de Camp to Vandeleur, to request he would move his Brigade as quickly as possible across that Bridge, so that he might meet with no interruption in his retreat, in the event of his being hard pressed.
Of the Centre Column, the Heavy Brigades of Lord Edward Somerset and Sir William Ponsonby had retired along the Charleroi road, and were taking up a position on some high ground, a little in rear of Genappe, on either side of that road. The detached Squadron of the 11th Light Dragoons (under Captain Schreiber), was withdrawn and directed to retire through the above town. The 23rd Light Dragoons were also withdrawn, and posted upon the ascent between Genappe and the position occupied by the two Heavy Brigades. The 7th Hussars continued on the south side of Genappe, as Rear Guard.
Neither the Centre, nor the Right, Column experienced any serious molestation in its retreat while on the French side of the Genappe: large bodies of Cavalry were seen in motion, but their Advanced Guards limited their attacks to skirmishing.
At length the 7th Hussars retired through Genappe, after having thrown out their Right Squadron, commanded by Major Hodge, as Rear Guard, to cover the retreat of the Centre Column, regulating its proceedings in conformity with such Orders as it might receive from Major General Sir William Dörnberg, who had been desired to superintend the movements of the Skirmishers. Major Hodge led out the Right Troop, under Captain Elphinstone, to skirmish, while Lieutenant Standish O'Grady, who commanded the Left Troop, held the high road, from which he had occasionally to send assistance to the former, and frequently to advance, to enable the Skirmishers to hold their ground, as their movements were difficult, through ploughed fields so soft that the horses always sank up to their knees, and sometimes to their girths. In this manner, every inch of ground was disputed, until within a short distance of Genappe.
Here Dörnberg informed Lieutenant O'Grady that he must leave him; that it was of the utmost importance to face the Enemy boldly at this spot, as the Bridge in the town of Genappe was so narrow that the Squadron would have to pass it in file; that he was to endeavour as much as possible to obtain time for drawing off the Skirmishers, but not to compromise his Troop too much. Lieutenant O'Grady then called in his Skirmishers, and advanced with his own Troop boldly up the road at a trot. The Cavalry immediately opposed to him, went about, followed by him for some distance; and he thus continued alternately advancing and retiring, until he saw all the Right Troop safe on the road in his rear. He then began to retire at a walk, occasionally halting and fronting, until he turned the corner of the town of Genappe: when he filed the men from the left, and passed through the place at a gallop. Upon the arrival of the Squadron at the opposite entrance of Genappe, it was posted between this point and the main body of the 7th Hussars, which had been drawn up on the road in a column of divisions, prepared to check the advance of the Enemy on his debouching from the town.
The British Left Cavalry Column continued its retreat, which was towards the little Bridge of Thuy, by deep narrow lanes, converted by the tremendous pour of rain into perfect streams. Vivian withdrew the 10th and 18th Hussars from the position he last occupied, but on their approaching the Genappe an interruption occurred in consequence of Vandeleur's Brigade not having effected its passage across the Bridge; and the delay became so great that he was induced to put about the 18th Hussars, with a view to their affording a Support to the 1st German Hussars, should they require it. In a short time after this, Vandeleur's Brigade resumed its progress: the 10th Hussars followed; and, as the 1st Hussars, with which Regiment Vivian himself was at the moment, continued to maintain a vigorous and effective skirmish, he ordered the 18th to resume its retrograde movement; having previously directed that some men of the 10th Hussars should be dismounted on reaching the opposite bank of the Genappe, and be prepared with their carbines to defend the passage, should the retreat of the remainder of the Brigade be severely pressed. After skirmishing some time, Vivian despatched a Squadron of the 1st German Hussars to the Bridge, and the moment he began to do so, the French Cavalry again pushed forward with so much boldness and rapidity as to interpose between the Left Squadron and the main body of the Regiment, and to compel that Squadron to pass the Genappe lower down than the Bridge over which the Brigade passed the little stream. Having ascertained that all was ready, Vivian galloped down the road to the Bridge with the remainder of the 1st German Hussars. The French followed them, loudly cheering, but as soon as the Hussars cleared the Bridge, and the Enemy's Dragoons reached it, some of the dismounted men that had been formed along the top of the opposite bank, in rear of a hedge, overlooking the Bridge and a hollow way, through which the road led from it up the ascent, opened a fire upon the foremost of the French Lancers that had come up to the other end of the Bridge, while the remainder of the 10th, and the whole of the 18th Hussars, were drawn up along the rising ground or bank. The good countenance here shown by Vivian's Brigade, combined with the soft and miry state of the ground after the thunderstorm had set in, completely checked the pursuit by the Enemy's Cavalry, which now turned towards the high road.