What Happened? Where the Heck is Mont St Jean?

French Supply Train in Camp, during the Waterloo campaign 1815
Florent Vincent
Source

Napoléon had mustered the equivalent of six combined arms corps (infantry, artillery, and cavalry) and four cavalry corps (cavalry and horse artillery) at the frontier with Belgium by early June. Roughly 125,000 men and over 300 cannon were ready to march against the enemy.

That enemy was composed of roughly 107,000 Anglo-Allied (English, Irish, Scots, Welshman, Dutchmen, Belgians, and various assorted Germans, not the least of which were the King's German Legion) troops under the Duke of Wellington and some 123,000 Prussians under Field Marshal Blücher. Napoléon had rough parity with the Prussians and outnumbered the Anglo-Allied army in both quantity and (IMHO) quality.

As can be seen below, Wellington's forces were spread from Brussels to Mons on a north-south line and from Genappe to south of Ghent on an east-west line. Each red block indicates an Anglo-Allied unit, the blue are the French, and the gray are the Prussians.

The Prussians were concentrated in four blocks of corps strength as can be seen on the map. They could concentrate forward near Ligny with Ziethen, which they did in real life, or fall back on Liege which led back to the Rhine and their supply bases.

I've circled in green the four locations where battles were fought during this campaign: Quatre Bras and Ligny on the 16th of June, then Mont St Jean and Wavre on the 18th of June. (No boys and girls, there was no battle fought at Waterloo, that was where Wellington had his headquarters and he liked the name, easy for an Englishman to pronounce, dontcha know. As he won the battle, he got to name it. Though the Prussians might argue that point, with good reason. They call it the battle of La Belle Alliance, the inn near Napoléon's position during the battle where Wellington and Blücher met as the French army fled down the road to Paris. Incidentally, La Belle Alliance translates to "the beautiful alliance." So named by the proprietor of said inn, apparently it came with his wife when they got married. The place still exists and was a night club, last I knew.)

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In real life, the French drove back the Prussian outposts on the 15th of June in the vicinity of Charleroi. The delay gave the Prussians time to concentrate three corps (Ziethen, Pirch, and Thielmann) in the area of Ligny. Napoléon brought up the equivalent of four combined arms corps (III Corps under Vandamme, IV Corps under Gérard, VI Corps under Lobau, and the Imperial Guard under Drouot) and most of three cavalry corps (the four cavalry corps are shown on the map in one block, the one labeled "Grouchy").

Napoléon sent II Corps (Reille) and elements of one cavalry corps with some Guard cavalry to drive off the Anglo-Allied units near Quatre Bras. D'Erlon, commanding I Corps was held in general reserve behind the II Corps. The Emperor took personal command at Ligny, Marshal Michel Ney commanded the left wing, the chaps going up against Quatre Bras.

The fighting at Ligny was bloody and brutal, no quarter was asked or given. At Quatre Bras, Ney let his troops have their breakfast before launching an attack on the crossroads around two in the afternoon.

Two. In the afternoon. (Kinda late, dontcha think?)

Meanwhile, the Emperor called on D'Erlon to bring his corps to Ligny, where he could fall on the rear of the Prussian right flank and complete that army's utter destruction. Ney recalled D'Erlon to Quatre Bras. So I Corps spent the battle marching back and forth, their intervention on either field would have been decisive, but their arrival at Ligny would have probably knocked the Prussians all the way back to Liege. (Field Marshal Blücher got lucky, he had his horse shot out from under him while leading an attack and went unnoticed in the gloaming, being ridden over by French cavalry at least twice.)

Now Blücher's chief of staff, Gneisenau, didn't trust the Duke of Wellington, his initial desire was to retreat on Ligny. He did think better of it and ordered a retreat on Wavre, where the Prussian army would be able to provide support to Wellington, who they knew would retreat when he got word of the Prussian defeat at Ligny. Wellington's army was absolutely no match for the combined forces under Napoléon.

So back they went, Wellington towards Mont St Jean, a position he was familiar with, and the Prussians to Wavre. Not an easy march to Mont St Jean for the Prussians but doable. (As they accomplished this in real life, they proved it to be doable. But had they had to fight their way there? No way. IMHO)

Napoléon was exhausted after Ligny. He decided to move against Wellington next, leaving Grouchy to chase down what the Emperor thought were the remnants of Blücher's army while he dealt with the Anglo-Allied army.

Grouchy's pursuit got a late start, mostly because of the Emperor wanting to review the troops and walk the field of what turned out to be his very last victory. Ney also dawdled at Quatre Bras, again having a leisurely breakfast while the Anglo-Allies scooted north as the heavens erupted in a spectacular thunderstorm. Heavy rain turned the fields and the side roads into muck, which did slow the pursuit of both wings.

The Anglo-Allies made it to Mont St Jean where they populated the ridge there and a number of sturdy farmsteads to oppose Napoléon's army coming up, albeit slowly, from the south.

Grouchy simply plodded along after the Prussians. Napoléon's orders had been to keep the tip of his sword at Blücher's backside. What Grouchy did more or less was wave a butter knife at him from a comfortable distance. A close pursuit might have caused the Prussians to disintegrate. The pursuit was anything but close.

At Mont St Jean, the 18th dawned wet and soggy. The ground was extraordinarily muddy and Napoléon's artillery chief recommended waiting to start the battle until after the ground had dried out some. So they waited, Napoléon reviewed the troops, then retired to rest his weary ass (he was still being bothered by piles, especially after having been in the saddle most of the 16th and a large part of the 17th.) So he left Ney in charge.

The French opened the battle (probably after 1300 hours) with a cannonade on the center of Wellington's line and a probe towards a rather large complex of farm buildings on Wellington's right flank. Place called Hougoumont, also known as the Chateau de Goumont. That place had a competent garrison, mostly British Guards and some German light infantry in the woods in front of the place.

History has it that Napoléon wanted to distract the British at Hougoumont, but his kid brother Jérôme, who commanded a division in II Corps, let his troops get carried away. The corps commander, Reille, did little to restrain Jérôme. So what should have been a sideshow sucked in a large part of II Corps.

On Napoléon's right, I Corps finally went into action, using an odd formation which massed the troops in great blocks. Few could fire their weapons, but as a way to get quickly over the field, it wasn't that bad of an idea. It nearly worked, but for the British cavalry's Union Brigade (made up of English, Scottish, and Irish troops) headlong attack at the head of the left most French column. Which completely disrupted them, causing them to flee back to their starting point.

The British cavalry chased them all the way to the gun line where they were counterattacked by French cavalry. In reality, Wellington traded a single cavalry brigade for 12 brigades of French infantry. Not a bad deal.

After that early success the French continued to pound the Anglo-Allied line. A number of Wellington's units fled the field, leading Marshal Ney to think that the Anglo-Allied army was retreating, so he launched most of his cavalry, thousands of horsemen, at the Anglo-Allied ridge. Where they were driven off by artillery and infantry fire from the infantry massed in squares, a pretty good all-round defense against cavalry.

The Battle of Waterloo: The British Squares Receiving the Charge of the French Cuirassiers
Henri Félix Emmanuel Philippoteaux¹ (PD)

Sometime in the early evening Napoléon came out of his misery and realized that Ney was thrashing. Though he had answered rudely when Ney had begged for infantry, "What does he expect me to do? Make them?" He decided to slap together some of the surviving units from I Corps (there were quite a few lying about). (Ignoring the fact that he still had the Imperial Guard in reserve. Though in all fairness, the Prussians were nearby and the Emperor knew it.)

A task group was put together to seize the farm complex of La Haye Sainte which stood just below the center of Wellington's position. There had been fighting around that place all day, but now the French got serious and the men of the King's German Legion, manning that post, ran out of ammunition. So they had no choice but to flee.

Source

At nearly the same time the Prussians were making their presence known on the French right flank, the Emperor had already sent the small VI Corps to that flank to stop the Prussians and had had to reinforce them with elements of the Imperial Guard.

As the sun set, as men screamed and died, as cannon and musket fire shattered the ear drums of the combatants as well as clogging the air with thick clouds of powder smoke, the Duke of Wellington allegedly muttered, "Give me night, or give me the Prussians." He could feel the morale of his army wavering.

That's about the time Napoléon sent his last reserve into the fight, elements of the Imperial Guard went up the ridge, were shattered by musket fire, and the French army went from being disciplined soldiers to a panicked mob. Fleeing back from whence they came.

Near Wavre, Grouchy and his two corps essentially kept one Prussian corps away from the main show. He basically did little or nothing. Had he tried to interpose his troops between Wavre and Mont St Jean, or launched attacks against the marching Prussians trying to cross the sodden terrain using bad roads, who knows what might have happened.

Well, we'll see, won't we?

¹ One of my favorite paintings though the terrain in the background is horribly inaccurate.