Napoleon lost the Battle of Waterloo on June 18, 1815, because of a cascade of problems that compounded throughout the day: rain-soaked ground that delayed his attack by hours, a failure to keep the Prussian army from reinforcing Wellington, reckless cavalry charges without infantry support, and a defensive position that neutralized France’s greatest advantage, its artillery. No single factor decided the outcome. Instead, each one narrowed Napoleon’s margin for error until he had none left.
Rain and Mud Cost Napoleon the Morning
Heavy rain fell through the night of June 17, leaving the battlefield waterlogged. Napoleon recognized immediately that the saturated soil would make his artillery ineffective, so at 5:00 a.m. he set the attack for 9:00 a.m. to let the ground dry. When 9:00 arrived, some French units still weren’t in position and the ground remained too soft. The main bombardment from the Grand Battery didn’t begin until around 1:00 p.m., a delay of roughly eight hours from first light.
Those lost hours proved devastating. Even once the guns opened fire, the soft earth swallowed cannonballs on impact instead of letting them bounce and skip through enemy ranks. This “ricochet fire” was normally what made Napoleonic artillery so lethal against massed infantry. Wellington’s troops, positioned behind the ridge and lying down, suffered practically no casualties from the bombardment. The weapon Napoleon relied on most was essentially taken out of the equation before the battle’s main phase even began.
Wellington’s Defensive Position
Wellington chose his ground carefully. He placed the bulk of his army on the reverse slope of a long ridge, meaning his troops were on the far side of the hill from the French. This simple positioning had two powerful effects: French artillery observers couldn’t see what they were shooting at, and French infantry advancing uphill had no idea what awaited them on the other side.
Wellington’s soldiers lay flat behind the crest until French columns crested the ridge, then stood up and delivered volleys of musket fire at close range. Columns that had marched uphill through mud, already exhausted and disordered, suddenly faced a wall of fire from troops they hadn’t been able to see moments earlier. This tactic was Wellington’s signature, and he had used it effectively throughout the Peninsular War. At Waterloo, combined with the mud that blunted artillery, it turned Napoleon’s standard approach of softening defenses with cannon fire and then sending in infantry columns into a grinding, costly failure.
Grouchy Never Arrived, but the Prussians Did
Napoleon had split his army after defeating the Prussians at Ligny on June 16. He sent Marshal Grouchy with roughly a third of his forces to pursue the retreating Prussian army and prevent it from linking up with Wellington. His orders were direct: “Pursue the Prussians, complete their defeat by attacking them as soon as you come up with them, and never let them out of your sight.”
Grouchy followed those orders too literally. He pursued the Prussians toward Wavre but failed to position himself between the Prussian army and the Waterloo battlefield. The critical mistake, however, may have been Napoleon’s as much as Grouchy’s. After their defeat at Ligny, the Prussians retreated north toward Wavre rather than east toward their supply lines in Prussia. This kept them within striking distance of Wellington. Prussian commander Blücher, after receiving word that Wellington would fight a defensive battle at Waterloo, resolved to send General von Bülow’s IV Corps to strike Napoleon’s right flank.
The Prussians began arriving on the battlefield in the late afternoon, opening an entirely new front that forced Napoleon to divert troops he desperately needed for his main assault. Grouchy, still engaged near Wavre miles to the east, never made it to Waterloo. The roughly 30,000 Prussian troops who reached the field transformed the battle from the one-front fight Napoleon had planned into a two-front fight he couldn’t sustain.
Ney’s Unsupported Cavalry Charges
Marshal Ney, commanding much of the French attack, launched massive cavalry charges against Wellington’s center during the mid-afternoon. The charges were premature and, critically, unsupported by infantry or artillery moving forward in coordination. French horsemen surged up the slope repeatedly, only to find Wellington’s infantry formed into squares, a formation that cavalry alone could not break. Without infantry to pour fire into those tightly packed squares, and without horse artillery keeping pace to blast gaps in them, the cavalry rode around the formations, took heavy losses, and withdrew, only to charge again.
Ney had shown this tendency before. At Quatre Bras two days earlier, he had ordered an unsupported cavalry charge of roughly 800 cuirassiers against British lines. That charge briefly seized the crossroads before being driven back by unbroken infantry squares. The pattern repeated at Waterloo on a far larger scale. Thousands of French cavalry horses and riders were exhausted in charges that achieved nothing permanent, and the infantry that could have exploited any breakthrough was never sent forward at the right moment.
The Hougoumont Drain
Napoleon originally intended the attack on the fortified farmhouse of Hougoumont, on Wellington’s right flank, as a diversion to draw Allied reserves away from the center. Instead, the fight for Hougoumont became a battle within the battle. French forces committed far more troops to capturing the farm complex than planned, while a relatively small Allied garrison held out all day behind its thick walls and hedgerows. What was supposed to be a feint became a resource sink, tying down French battalions that were needed elsewhere on the field.
The Imperial Guard’s Final Collapse
By early evening, Napoleon committed his final reserve: the Imperial Guard, the elite of the French army. These were veterans whose mere appearance on a battlefield had historically caused enemy formations to waver. Napoleon sent battalions of the Middle Guard up the slope toward Wellington’s line in a last attempt to break through before the Prussian pressure on his right became overwhelming.
The Guard advanced into a trap. As the columns of chasseurs crested the ridge, the British 52nd Regiment executed a rapid flanking march across the slope, positioning itself on the column’s exposed side. The 52nd delivered a series of devastating volleys that crushed the formation. After a brief, disorganized attempt to return fire, the Guard broke and ran. When the rest of the French army saw the Imperial Guard, troops who supposedly never retreated, streaming back down the hill, morale collapsed across the entire line. The cry went up: “La Garde recule!” The Guard retreats. Within minutes, the French army disintegrated into a rout.
Napoleon’s Own Condition
There is medical evidence that Napoleon was physically impaired on June 18. He had fought effectively at Ligny just two days earlier, but at Waterloo he appears to have been suffering from severely painful thrombosed hemorrhoids. While it’s impossible to measure exactly how much this affected his decision-making, contemporaries noted he was not himself that day. For a commander whose greatest strength was personal energy and rapid, decisive action, any physical limitation mattered. He spent portions of the battle away from the front, delegating tactical decisions to subordinates like Ney who made costly errors he might otherwise have corrected.
Why It All Added Up
Napoleon entered the Waterloo campaign with roughly 128,000 troops in his Army of the North, facing combined Allied and Prussian forces that significantly outnumbered him. His strategy of dividing his enemies and defeating them separately was sound, and it nearly worked at Ligny and Quatre Bras on June 16. But “nearly” left both enemy armies intact and able to converge on him two days later.
At Waterloo itself, the rain stole his artillery advantage. Wellington’s positioning neutralized what firepower remained. Ney wasted the cavalry. Hougoumont consumed troops meant for the main attack. Grouchy failed to prevent the Prussian arrival. And when Napoleon finally played his last card, the Imperial Guard, it was too late in the day, against a defensive line that had held for hours, with fresh Prussian forces already rolling into his flank. Each problem might have been survivable on its own. Together, they were fatal.