At 3 P.M. that day Wellington was apprised of these movements, but so certain was he of the soundness of his dispositions that he feared nothing. Learning that no French troops were moving in the direction of Mons, he knew that his right flank was safe, so at 5 P.M. he issued orders for a general concentration of his force towards Quatre Bras—the point where the Nivelles-Ligny road crossed the road from Charleroi to Brussels—and at 10 P.M. he supplemented these orders by detailed instructions as to routes and objectives. Then he attended the famous ball given by the Duchess of Richmond in Brussels, whereat a great many British officers were present, though all had been warned that they were to leave early and join their regiments marching to the front. Straight from the festive scene, therefore, many rode all night to overtake the troops only as they were becoming engaged with the enemy.

At daybreak on the 16th the 51st (with Mitchell's brigade) left Grammont for Braine le Comte, where, after a weary march, it halted for the night in pouring rain. During the march the sounds of guns were distinctly heard in the distance, yet no one in the regiment knew what was taking place, or the whereabouts of the enemy. But not far away stirring events had been in progress. At 11 A.M. Wellington, riding from Brussels, had reached the position which his advanced troops were taking up at Quatre Bras, though by that time only some 7000 Dutch and Belgians, under the Prince of Orange, had arrived. Fortunately, however, Napoleon appeared to be directing all his energies against Blücher's 80,000 Prussians, in the neighbourhood of Ligny, and Wellington rode across to confer with the Prussian Field-Marshal, eventually agreeing to go to his assistance at 4 P.M., if not himself attacked.

Wellington then returned to Quatre Bras, and within a couple of hours realised that the Prussians would have to look after themselves; for Napoleon, aiming at a double victory, sent Ney against Wellington early in the afternoon, and the battle which raged around Quatre Bras for the remainder of the day only ended in a victory for Wellington by the timely arrival of the reserves from Brussels. Blücher, in the meanwhile, had been severely handled by Napoleon, who, after a bloody conflict of nearly six hours, succeeded in breaking the centre of the Prussian line and driving the defeated army from the field. But of the forced retreat of his Prussian allies from Ligny Wellington heard nothing definite until next morning, when he learned that Blücher had retired upon Wavre.

No sooner did Wellington become aware of the Prussian retreat than he decided to fall back from Quatre Bras to the position at Waterloo which he had had in his mind all along, and at about 10 A.M. on the 17th June he sent word to Blücher that he would fight at Waterloo if a Prussian corps would join him there. He then issued orders for the retirement from Quatre Bras, and sent instructions to Prince Frederic's Dutch-Belgians and such troops of the 4th Division as were at Braine le Comte or on the road to Nivelles to assemble at the former of these two places and await orders, while all other troops were to retire at once to Waterloo. Now it happened that Mitchell's brigade alone of the 4th Division, marching early from Braine le Comte, had reached Nivelles before the order arrived, and thus avoided sharing in the ill-luck which befell the remainder of the division—viz., being posted on the flank at Tubize, near Hal, while the great victory of the 18th June was being won.[81] Mitchell, therefore, paraded his brigade with the 2nd Division, already at Nivelles; and at noon the 51st was marching north by the Brussels road.

The march of the afternoon was hot and dusty, and was made all the more disagreeable by the road frequently becoming blocked by troops, guns, wagons, and ambulances withdrawing from Quatre Bras. The prospects of a fight, however, kept the men going, and the sight of some French columns in motion during the afternoon put new life into them. It was evident that an engagement could not be long delayed, and many imagined that it would take place before nightfall. Towards evening Mitchell marched his brigade on to that part of the position allotted to it—on the extreme right near Braine la Leud, and there the 51st and the other regiments of the brigade bivouacked. In all directions troops could be seen moving into position; and though darkness was approaching it still seemed as if the fight could not be postponed till the morrow. Masses of French troops were visible at no great distance, and a few British guns were already opening fire on some of the enemy's infantry, while parties of cavalry were briskly engaged in more than one part of the field.

But the night closed in without matters going further, and it was a night not easily forgotten by those who slept out in it. Rain fell in torrents, so that the bivouacs became a sea of mud, and the soldiers, lying out in the open, were drenched to the skin. When at length day broke and the heavy rain ceased, the situation became fully apparent, and no doubt remained as to the severity of the coming struggle. Less than a mile separated the two great armies, drawn up and facing one another. Between them lay a shallow valley, some two or three miles in length, and averaging half a mile in width, the sides sloping gently, but being everywhere uneven and undulating. The trend of the valley was east and west, and Wellington's army occupied the northern crest and ground in rear, slightly in advance of the village of Mont St Jean; while the French were in position on the southern crest. From south to north, and dividing each position into two almost equal parts, ran the great paved causeway from Charleroi to Brussels. Such was the field whereon was fought the memorable battle of Waterloo, so named from the village a little in rear of Mont St Jean; and within that cramped area there were at one time engaged no fewer than one hundred and eighty thousand combatants.

It is not proposed to treat here of the battle of Waterloo in detail—a task to which numerous bulky volumes have been devoted,—but in describing the small part played in the fight by Lieut.-Colonel Sam Rice and his regiment, it will be necessary at any rate to sum up the situation at various times, in order to make the narrative complete. Still it may be said at once that the bulk of Mitchell's brigade kept to the one part of the field throughout the day, at times gaining ground, at times forced back, yet ever awaiting attack in the vicinity of Hougoumont. The brigade was weak in numbers, mustering no more than 1800 bayonets, of which the 51st supplied 540. The duty allotted to Mitchell was an important one, since Wellington considered it probable that Napoleon would attempt to turn his right flank and push through to Brussels by way of the road through Hal, and it was for that reason that he had detached the Dutch-Belgians and part of the 4th Division (numbering in all some 18,000 men) to the neighbourhood of Hal. These troops were some five miles from the field of battle, and at the outset Mitchell's brigade was called upon to hold in check any determined movement of the enemy in this direction until fresh dispositions could be made.

Wellington had taken up a strong defensive position, with most of his troops drawn back below the actual crest, and with his reserves well concealed by the folds of the ground. Napoleon, on the other hand, deigned to little concealment, and sought to break down his opponents' defences by sheer weight of numbers. At a little before noon the fight commenced, Napoleon sending forward his brother, Prince Jerome, against the advanced post of Hougoumont, which, as the key of the position, was strongly held by the Allies. At the same time an artillery duel opened all along the line, and a tempest of shot and shell raged across the valley; but the defenders of Hougoumont, reinforced by the whole of Byng's British Guards, resisted every onslaught of the French columns, even though parties of the enemy established themselves close up to the buildings and set them on fire. Almost continuously during the afternoon the attacks on this vital point went on, and so numerous at times were the assailants that they were able to overlap it and threaten the right of the Allies' main line. Here Mitchell's men came into action, and assisted in forcing back the assailants.

Early in the day Mitchell had advanced several companies, for the purpose of closing the gap between Hougoumont and Braine la Leud, and one company of the 51st was posted close to an abatis which had been placed across the main road a little in rear of the entrance to the avenue of Hougoumont. Four other companies of the regiment were extended farther to the right, along the hollow way leading to Braine la Leud, with instructions to engage the enemy's skirmishers as they advanced, and then to endeavour to harass with heavy musket fire the solid columns following their skirmishers. As had been expected, the French columns came on, covered by skirmishers, but so advantageous was the ground over which they advanced, and so high the standing corn through which they moved, that the companies of the 51st could not observe their approach until they were almost upon them. Then, rising, the British soldiers poured in their fire at forty paces, and, cheering wildly, dashed forward at the charge. And the impetuous onslaught had the desired effect, for the enemy, although supported by cavalry, were beaten back. The four companies of the 51st were then ordered to retire some two hundred yards, and rejoin the regiment.

While this was in progress, Napoleon was busy making preparations for his grand assault, designed to break the left centre of the British position. For this great effort, seventy-four guns were moved up, so as to bring their fire to bear, at a range of less than half a mile, on the Allies; and Marshal Ney was placed in command of 18,000 men in four columns, supported by Kellerman's cavalry division. Napoleon hoped that this combined attack would be final and decisive; that, having captured the advanced post of La Haie Sainte, the columns would be able to sweep onwards to Mont St Jean, cut off Wellington from Brussels as well as from the Prussians coming from the direction of Wavre, and thus make victory complete. At 1 P.M. Ney's masses of columns moved down into the valley, and passed the seventy-four guns, which immediately opened fire over their heads, and caused havoc in the ranks of the Allies. Three of the columns pressed forward towards the Allies' centre, while the third moved away north-east, with the intention of driving in the left flank. Whether by design or by accident, Ney's principal attack was directed against the portion of the front line held by Bylandt's brigade of Dutch and Belgians, and no sooner did the French skirmishers, covering the advance of the columns, begin to make use of their muskets than panic seized their adversaries, who turned and fled in disorder. Then was Wellington's forethought, as well as the wisdom of his dispositions, apparent, for doubting the loyalty of the Dutch-Belgians, he had been careful to support them everywhere by British brigades, and here, close in rear, stood Picton's division, ready to take the place of the disloyal or cowardly Dutch-Belgians.