The approach of the multitudinous Russian, Austrian, Bavarian, and other foes of the French Emperor to the Rhine was necessarily slow; but the two most active of the allied powers had occupied Belgium with their troops, while Napoleon was organizing his forces. Marshal Blucher was there with one hundred and sixteen thousand Prussians; and, before the end of May, the Duke of Wellington was there also with about one hundred and six thousand troops, either British or in British pay. [Ibid. vol. i. chap. 3. Wellington had but a small part of his old Peninsular army in Belgium. The flower of it had been sent on the expeditions against America. His troops, in 1815, were chiefly second battalions, or regiments lately filled up with new recruits. See Scott, vol viii. p. 474.] Napoleon determined to attack these enemies in Belgium. The disparity of numbers was indeed great, but delay was sure to increase the proportionate numerical superiority of his enemies over his own ranks. The French Emperor considered also that "the enemy's troops were now cantoned under the command of two generals, and composed of nations differing both in interest and in feelings." [See Montholon's Memoirs, p. 45.] His own army was under his own sole command. It was composed exclusively of French soldiers, mostly of veterans, well acquainted with their officers and with each other, and full of enthusiastic confidence in their commander. If he could separate the Prussians from the British, so as to attack each singly, he felt sanguine of success, not only against these the most resolute of his many adversaries, but also against the other masses, that were slowly labouring up against his eastern dominions.

The triple chain of strong fortresses, which the French possessed on the Belgian frontier, formed a curtain, behind which Napoleon was able to concentrate his army, and to conceal, till the very last moment, the precise line of attack which he intended to take. On the other hand, Blucher and Wellington were obliged to canton their troops along a line of open country of considerable length, so as to watch for the outbreak of Napoleon from whichever point of his chain of strongholds he should please to make it. Blucher, with his army, occupied the banks of the Sambre and the Meuse, from Liege on his left, to Charleroi on his right; and the Duke of Wellington covered Brussels; his cantonments being partly in front of that city and between it and the French frontier, and partly on its west their extreme right reaching to Courtray and Tournay, while the left approached Charleroi and communicated with the Prussian right. It was upon Charleroi that Napoleon resolved to level his attack, in hopes of severing the two allied armies from each other, and then pursuing his favourite tactic of assailing each separately with a superior force on the battle-field, though the aggregate of their numbers considerably exceeded his own.

The first French corps d'armee, commanded by Count d'Erlon, was stationed in the beginning of June in and around the city of Lille, near to the north-eastern frontier of France. The second corps, under Count Reille, was at Valenciennes, to the right of the first one. The third corps, under Count Vandamme, was at Mezieres. The fourth, under Count Gerard, had its head-quarters at Metz, and the sixth under Count Lobau, was at Laon. [The fifth corps was under Count Rapp at Strasburg.] Four corps of reserve cavalry, under Marshal Grouchy, were also near the frontier, between the rivers Aisne and Sambre. The Imperial Guard remained in Paris until the 8th of June, when it marched towards Belgium, and reached Avesnes on the 13th; and in the course of the same and the following day, the five corps d'armee with the cavalry reserves which have been mentioned, were, in pursuance of skilfully combined orders, rapidly drawn together, and concentrated in and around the same place, on the right bank of the river Sambre. On the 14th Napoleon arrived among his troops, who were exulting at the display of their commander's skill in the celerity and precision with which they had been drawn together, and in the consciousness of their collective strength. Although Napoleon too often permitted himself to use language unworthy of his own character respecting his great English adversary, his real feelings in commencing this campaign may be judged from the last words which he spoke, as he threw himself into his travelling carriage to leave Paris for the army. "I go," he said, "to measure myself with Wellington."

The enthusiasm of the French soldiers at seeing their Emperor among them, was still more excited by the "Order of the day," in which he thus appealed to them: