1815 battle during the War of the Seventh Coalition
 Hundred Days: ;br ;Waterloo campaign
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The Battle of Quatre Bras was fought on 16 June 1815, as a preliminary engagement to the decisive Battle of Waterloo that occurred two days later. The battle took place near the strategic crossroads of Quatre Bras and was contested between elements of the Duke of Wellington's Anglo-allied army and the left wing of Napoleon Bonaparte's French "Armée du Nord" under Marshal Michel Ney. The battle was a tactical victory for Wellington (as he possessed the field at dusk), but because Ney prevented him going to the aid of Blucher's Prussians who were fighting a larger French army under the command of Napoleon Bonaparte at Ligny it was a strategic victory for the French.
Prelude.
Facing two armies (Wellington's arriving from the west and the Prussians under Field Marshall von Blücher from the east), Napoleon's overall strategy was to defeat each in turn, before these forces could join. Napoleon intended to cross the border into what is now Belgium (but was then part of the United Kingdom of the Netherlands) without alerting the Coalition leaders and drive a wedge between their forces. He planned to defeat the Prussian army, forcing them to retreat eastward, and then turn to engage Wellington, driving his army back to the Channel coast.
Napoleon recognized that, if Wellington's Anglo-allied army could join with the Prussians, the combined force would be larger than his French army. The crossroads at Quatre Bras therefore became a strategic position, since if the French held this interchange, they could prevent Wellington's forces from moving south-eastward along the Nivelles-Namur road towards the Prussians, where Napoleon was planning to engage von Blücher on 16 June at Ligny.
Although the Coalition commanders were receiving intelligence, Napoleon's planning was initially successful. Wellington remarked: "Napoleon has humbugged me, by God; he has gained twenty-four hours' march on me."
While Wellington's instructions at the start of the campaign were to defend Brussels from the French, he was not sure what route Napoleon's army would follow; he also received (false) reports of a flanking maneuver through Mons to the southwest. Wellington first received reports of the outbreak of hostilities at around 15:00 on 15 June from the Prince of Orange, a Coalition commander. Within the next few hours, he received additional news that the French had skirmished early that morning with the Prussian First Corps under Lieutenant-General Graf von Zieten at Thuin (near Charleroi). These reports prompted Wellington at 18:00 to draft initial orders to concentrate his army. However, he was still uncertain precisely where to bring his forces together, and it was not until almost midnight, when he learned that the front near Mons was clear, that he ordered his army to move towards the Prussians.
This nine-hour delay meant it was too late for him to move his army in sufficient strength to provide von Blücher with support on 16 June at the Battle of Ligny. Wellington did not order his entire army to Quatre Bras on 16 June, still suspecting a flanking maneuver through Mons. The headquarters of the Anglo-allied First Corps (Prince of Orange's), however, decided to ignore Wellington's order that it should assemble in and around Nivelles, instead opting to take the initiative and converge on Quatre Bras.
Napoleon's original plan for 16 June was based on the assumption that the Coalition forces, which had been caught off guard, would not attempt a risky forward concentration; he intended therefore to push an advanced guard as far as Gembloux, for the purpose of feeling for and warding off von Blücher. To assist in this operation, the reserve would move first to Fleurus to reinforce Marshal Grouchy who was tasked with driving back the Prussian troops. However, once the French were in possession of Sombreffe, Napoleon planned to swing the reserve westwards to join with Marshal Ney, who—it was supposed—would have by that time secured the Quatre Bras crossroad.
Accordingly Marshal Ney, to whom III Cavalry Corps (Kellermann) was now attached, was to mass at Quatre Bras and push an advance guard northward of that place, sending a connecting division at Marbais to link him with Grouchy. The center and left wing together would then make a night-march toward Brussels. The Coalition forces would thus be forcefully separated, and all that remained would be to destroy each in detail. Napoleon now awaited further information from his wing commanders at Charleroi, where he massed the VI Corps (Lobau's), to save it, if possible, from a harassing countermarch, as it appeared likely that it would only be needed for the march to Brussels.
On 15 June as the Prussian I Corps withdrew towards Ligny, there was a danger for the Coalition forces that Ney would be able to advance through Quatre Bras and take his objectives with little or no Coalition opposition. At the headquarters of the I Corps at Genappe (about five kilometres (3 miles) from Quatre Bras), Major-General Jean Victor de Constant Rebecque, chief of staff to the Prince of Orange, realized the danger and ordered Lieutenant-General Hendrik George de Perponcher Sedlnitsky, the commander of the 2nd Dutch Division, to dispatch his 2nd Brigade (Prince Bernhard of Saxe-Weimar-Eisenach) to occupy Quatre Bras. This brigade, consisting of two regiments from Nassau, arrived at about 14:00 on 15 June. Prince Bernhard was able to deploy prior to the arrival of the first French scouts, lancers of the Guard Light Cavalry Division (Lefebvre-Desnouettes) who approached Quatre Bras. These French lancers were engaged at Frasnes, after which the Nassauers retreated to the Bois de Bossu, a thick patch of forest near Quatre Bras. "6:30 p.m. – some accounts say 5:30" General Lefebvre-Desnouëtte requested infantry support, but as night was approaching, and his infantry was strung out along Brussels-Charleroi road, Ney declined the request, instead deciding to camp for the night and approach Quatre Bras in force the following day. Early on the evening of 15 June, instead of obeying Wellington's order to concentrate the I Corps at Nivelles (which would have meant that the force occupying Quatre Bras would be abandoning the position), Rebecque ordered the 1st Brigade (Van Bylandt's brigade) of the 2nd Dutch Division to reinforce Prince Bernhard's 2nd Brigade.
By countermanding a direct order from Wellington and using his own initiative, Rebecque was responsible for the Battle being fought at Quatre Bras on the following day, thereby preventing the French from keeping the two coalition armies apart and destroying each of them in detail.
Ney spent the morning of 16 June massing his I and II corps, and reconnoitering the enemy at Quatre Bras, who, he was informed, had been reinforced. But up till noon he took no serious steps to capture the crossroads, which he could have done with relative ease. In the meantime, Grouchy reported from Fleurus that Prussians were coming up from Namur, but Napoleon does not appear to have attached much importance to this report. He was still at Charleroi when, between 09:00 and 10:00, further news reached him that hostile forces had concentrated at Quatre Bras. He at once wrote to Ney saying that these could only be some of Wellington's troops, and that Ney was to concentrate his force and crush what was in front of him, adding that Ney was to send all reports to Fleurus. Then, leaving Marshal Lobau's force provisionally at Charleroi, Napoleon hastened to Fleurus, arriving about 11:00.
Meeting at the Windmill of Bussy.
Shortly after 11:00, Wellington observed that the French were not in any great force at Frasnes (south of Quatre Bras). At the same time, accounts reached him that the Prussians, in position at Ligny, were being menaced by the advance of a considerable French force. Wellington, accompanied by his staff and a small escort of cavalry, rode off to hold a conference with von Blücher, whom he met at the Windmill of Bussy (often referred to as the Windmill of Brye) between Ligny and Brye. Because this windmill was at the highest point of the Prussian position, the leaders were able to observe the French preparatory deployments prior to their attack.
These observations led Wellington to conclude that Napoleon was bringing the main force of his army to bear against the Prussians; he at once proposed to assist von Blücher by first advancing straight upon Frasnes and Gosselies, as soon as he was able to concentrate sufficient force, and then attacking the French from their left and rear, thus providing a powerful diversion to aid the Prussians, since von Blücher's right wing was the weakest and most exposed, and considering Napoleon's movements was the most likely to be attacked.
The primary sources do not agree on what was said at the meeting. They all agree that Wellington promised aid to Blücher, but they disagree on whether Wellington made an unequivocal promise of aid, or whether Wellington made it clear that his ability to give timely assistance to Blücher was only possible if his forces were not engaged before he could send aid.
Siborne, writing from eyewitness accounts, records it thus:
 ;templatestyles src="Template:Blockquote/styles.css" / ;"Upon a calculation being made, however, of the time which would elapse ere the Duke would be able to collect the requisite force for undertaking this operation, and of the possibility of Blucher being defeated before it could be carried into effect, it was considered preferable that Wellington should, if practicable, move to the support of the Prussian Right by the Namur road. But a direct support of this kind was necessarily contingent on circumstances, and subject to the Duke's discretion. The latter having expressed his confident expectation of being enabled to afford the desired support, as also of his succeeding in concentrating, very shortly, a sufficient force to assume the offensive, rode back to Quatre Bras."
Combatants.
At the beginning of the battle the left wing of the "Armée du Nord", with 18,000 men (including 2,000 cavalry and 32 guns) under Marshal Michel Ney, faced 8,000 infantry and 16 guns, under the command of William, Prince of Orange. The Dutch (with the Nassauers of 2nd Brigade) were thinly deployed south of the crossroads of Quatre Bras. Fresh allied troops started to arrive two hours later, along with Wellington, who took over command of the allied forces. As the day wore on, fresh Dutch, British and Brunswickers arrived faster than fresh French troops (who eventually numbered about 24,000).
Battle.
Fighting started late in the afternoon on 15 June, when the Elba squadron, a small Polish lancer unit consisting of only 109 men and officers, tried to attack the allied forces from the direction of Frasnes. These forces consisted of the II/2nd Nassau regiment and Bijlevelds horse artillery. The Dutch and Nassau commanders had taken precautions, however, and the Lancers were greeted by canister and volley fire, losing some men and horses before retiring to Frasnes. Patrols were sent out and the positions were kept until the next morning.
From 5 AM on 16 June there were continuous skirmishes between Allied and French forces, in which neither side managed to get an advantage. Some Prussian hussars, cut off from their main body, skirmished with the Red Lancers, but they disengaged after Bijleveld's artillery once again drove the lancers back. Two companies of Nassau infantry advanced towards Frasnes, but this time the French pushed them back. Some time after 6 a.m., after the Prince of Orange arrived, the skirmishes stopped.
The real battle began with the French attack around 14:00 hours. Ney massed a battery of 22 guns and started bombarding the Coalition positions. Swarms of skirmishers preceded the French columns as they attacked. The Dutch picket line of the 2nd Division (Sedlnitsky) greeted them with musket volleys, but it was outnumbered and those east of the Brussels highway were at once forced back by the mass of men moved against them. The Nassauers of 2nd Brigade (Prince Bernhard of Saxe-Weimar) retreated to Grand-Pierrepont farm and Dutch troops of the 1st Brigade (Bylandt) to Gemioncourt, but the allies managed, however, to hold the wood. Facing three infantry divisions and a cavalry brigade, the situation became desperate for the 2nd Division.
At around 15:00 the 5th British Infantry Division (Picton) and the 3rd Dutch Light Cavalry Brigade (Baron van Merlen) arrived. The Duke of Wellington came back from his meeting with