At 11 A.M. Ney received from Napoleon a letter giving him detailed instructions as to the movements of the French army. The Emperor told Ney that he intended attacking the Prussians at Ligny, driving them back on Gembloux. Ney was then to march on Brussels, and Napoleon, marching by the Sombreffe-Quatre-Bras road with his Imperial Guard, would support him. Thus, according to the letter, Ney’s movements were to wait upon Napoleon’s. This interpretation was some cause of Ney’s delays on the 16th.
Soon after the receipt of Napoleon’s letter, Ney received an order from Soult, chief of the Staff, directing him to move the First and Second Corps, and Kellermann’s Cavalry, on Quatre-Bras, drive back the enemy, and reconnoitre as far as he could towards Nivelles and Brussels; also to push a division to Genappe, and another towards Marbais, so as to open communication with Napoleon’s left between Sombreffe and Quatre-Bras. Napoleon’s intention was to reach Brussels by daybreak on the 17th, having defeated the Prussians, and Ney having defeated the English!
In accordance with this order, Ney sent instructions to Reille and d’Erlon. These were to the following effect:—The First, Second, and Third Divisions of d’Erlon’s Corps were to move to Frasnes; the Fourth Division of that Corps, with Piré’s Cavalry, was to move to Marbais; Kellermann’s Cavalry Corps to Frasnes and Liberchies.
Just at this time, a message from Reille reached Ney, stating that Girard (not Gérard, who commanded the Fourth Corps) had sent in a report that strong columns of Prussians were moving along the Namur-Nivelles road, with heavy masses behind them. (These were Pirch’s I. troops deploying at St Amand and Ligny.) Reille had seen Napoleon’s letter to Ney, and read its contents, but he wrote to Ney that he would wait the latter’s instructions, while he prepared his troops for instant march. Another order from Napoleon reached Ney at this moment. It stated that the Marshal was to unite the First and Second Corps with Kellermann’s Cavalry, and drive the enemy from Quatre-Bras, thus distinctly emphasising the previous order. The Emperor, who thought that Ney would then have an ample force to crush any troops which could be in front of him, stated that Grouchy was about to move on Sombreffe.
Girard’s report as to the Prussian columns on the Namur road made Ney doubly anxious for his position. He therefore again sent urgent orders to Reille and d’Erlon to hasten up. At 2 P.M., in the belief that d’Erlon must be close behind, he moved to the attack of the Anglo-Dutch position with three infantry divisions (Bachelu’s, Foy’s and Jerome’s, of Reille’s Corps) and Piré’s Division of Light Cavalry, with 5 batteries—a strength of 18,000 men and 40 guns. Opposed to him were the 7,000 infantry and 16 guns of the Prince of Orange.
It is not proposed to give an account of the battle of Quatre-Bras. It has been shown what an opportunity Ney had lost by not attacking earlier, and what his reasons were for not doing so. Picton’s Division and the Duke of Brunswick’s Division arrived early in the afternoon, and Wellington took over the command. These reinforcements, to which were added towards the close of the day, Alten’s Division, Cooke’s Division, two more Brunswick battalions and a battery of Brunswick artillery, gave Wellington a superiority in numbers over Ney, who was only reinforced by Kellermann’s Cavalry Corps during the battle. D’Erlon’s Corps had, in the meantime, been wandering between Ligny and Frasnes.
In its results the battle of Quatre-Bras was of great importance to both sides. Although Ney had not obtained possession of Quatre-Bras, and had not defeated Wellington’s troops, nor driven them back on Brussels, yet he had effectually prevented Wellington joining with Blucher’s right. He had not been guilty of disobeying orders, and he himself did not feel confident of victory when he attacked on the afternoon of the 16th. On the other hand, Wellington had, by his masterly defence, completely frustrated Ney’s object. He was now in full possession of Quatre-Bras; he had gained a brilliant victory, and his divisions were still coming up from behind. Should he receive news of a Prussian victory at Ligny, he was prepared to attack Ney next morning, and, if successful, to join Blucher’s right wing and fall upon Napoleon’s left. If the Prussians were defeated at Ligny, he was ready to fall back and take up a position where Blucher could join him, and together they would attack Napoleon’s combined forces.
To turn to events upon the Prussian side, Blucher’s decision to stand at Ligny was determined by several strategical considerations. Firstly, the position he chose communicated with Wellington’s left by 6 miles of very good road, along which co-operation on either hand could be easily effected. Secondly, he guarded the communications with Aix-la-Chapelle and the Prussian States. Thirdly, if the Allies should be defeated both at Quatre-Bras and at Ligny, then two parallel lines of retreat, the one upon Mont St Jean towards Brussels, and the other upon Wavre towards Louvain, were available, which would render possible a junction near the forest of Soignies. Fourthly, if Napoleon had advanced against Wellington by way of Mons, the Prussians, by concentrating at Sombreffe, could have marched to the Duke’s assistance, leaving Zieten to watch Charleroi and the neighbourhood. Fifthly, if Napoleon had advanced on Namur, the Third Corps (Thielemann’s) could have retreated as did Zieten’s, and allowed time and protection for the First, Second, and possibly the Fourth Corps, while Wellington moved to join the Prussian right.
The situation of the Allied armies was not exactly that of the Austrians and Sardinians in Italy in 1796-97; there was the possibility of striking at their point of junction and of beating each army separately, but the short and excellent line of communication between the points of concentration of Wellington’s and Blucher’s armies, namely, the Quatre-Bras-Sombreffe road, afforded each army such easy and rapid means of effecting a junction, although, in fact, it was not actually used as a means of co-operation, that there was a “moral” influence in it which went a long way towards defeating Napoleon’s object. This may sound somewhat exaggerated; but what was it that made Ney uneasy for his own right flank on the 15th-16th, before he attacked? The report sent by Girard that Prussian columns were on that road. What was Napoleon’s fear during the battle of Ligny? That Wellington would send a force from Quatre-Bras to join Blucher’s right, along this road. What was the chief advantage in Wellington’s position at Quatre-Bras? This road again, which afforded a means of joining the Prussians at Ligny, had the occasion arisen. And in what way was this road of use to Blucher at Sombreffe? He could co-operate with Wellington if Napoleon had attacked viâ Mons.
Blucher had decided to fight at Ligny, even though he had little hope of the arrival of Bulow’s Corps in time to join the battle. For he believed that Napoleon’s forces were not superior to his own in numbers; he had selected the position previously, and had had it surveyed carefully; he hoped that he would be able to hold his own either until Bulow arrived, or until night put an end to the fight. In the event of the Fourth Corps reaching the field in time to take part, the extra weight in numbers would decide in Blucher’s favour, or else the Corps would attack Napoleon’s right flank at a time when his troops would be most fatigued. Or again, if night came on, sufficient time would have been gained for Bulow’s arrival to be made certain before daybreak next day, when a successful attack on the French might confidently be expected. In both cases, any pressure on Wellington would be relieved, so that the Anglo-Dutch Army might combine with Blucher to overwhelm the whole of Napoleon’s forces. Thus Blucher reasoned.