British troops defending Hougoumont
The first move of the battle finally came at 11:30am. This was an assault on the garrison at Hougoumont by Reille's Second Corps, initially intended as a means of distracting Wellington's attention from his centre. Napoleon seems to have hoped that Wellington would reinforce the farmhouse at the expense of the centre of his line but also hoped to clear this obstacle to allow an all-out assault across the whole front. However, the first attack was repulsed and so were another two. In fact, Hougoumont held out for most of the day, drawing the attention of some 14,000 French, the entire Second Corps. This was at the expense of only a couple of British battalions. The result was that the plan to weaken the Allied centre failed and throughout the day, Hougoumont proved to be a serious obstacle to any attack to the west of the Brussels road.
At 1pm, the great artillery bombardment began. This coincided with the first sighting of troops far to the east. It soon became clear that these were Bulow's First Corps of Prussians and not Grouchy's troops as Napoleon had hoped and expected. The artillery bombardment lasted for half an hour and was intended to soften up the Allied line in preparation for the advance of D'Erlon's First Corps. However, Wellington's position meant that his Allied troops were relatively unscathed by the time D'Erlon rolled forward at 1:30pm. Some 8,000 French infantry were met by Allied artillery and the infantry of Picton's division, mostly veterans of Spain. A Belgian brigade immediately routed but the French faired less well against the British troops. Nevertheless, the weight of the French attack looked to be too much for Picton, who was himself killed in the fighting, and a French Curassier brigade had overrun a Hanoverian battalion and were threatening the Allied centre. At this point, Wellington sent Lord Uxbridge and his heavy cavalry forward to salvage the situation.
Somerset's Household Brigade and Ponsonby's Union Brigade surged forward, passing the German infantry in squares and sweeping through the curassiers who were spent after their uphill charge. The next stop was D'Erlon's troops who were still drawn out in column, ready for attack. The result was carnage. Three of the four French divisions were routed and 3000 men were captured. If the British cavalry had stopped there and regrouped, it would have been a spectacular success. They didn't. Instead, they swept forward in a wild charge and headed straight for the heart of the French line, elated by their success in the initial charge. They soon met Napoleon's heavy cavalry and lancers and were decimated. Less than half made it back to the Allied line and Wellington's only mobile reserve was lost.