Napoleon the First had escaped from the Isle of Elbe. Cheered by his ancient soldiers, he soon entered Paris followed by a large army.
 

To put down Bonaparte the Allies formed against him six armies: the English and Dutch- Belgian army commanded by Wellington marched to Maubeuge; the Prussian army under Blücher marched to Givet, that of Schwarzenberg threatened Sarreguemines; the Russian army under Barclay de Tolly had in view Saarbrück; the Austrian Army under Frimont marched towards Lyon, and finally the Austro-Piedmontese army under Brachi, destined to invade La Provence. That made in all a force of 630,000 men against which Napoleon could hardly bring forward more than 125,000 men.
 

The allied armies had to march at once upon Paris as arranged by a plan made in the month of April, but of which the execution had to be put back to the first days of July.
 

The aim of Napoleon was to prevent the concentration of the English and the Prussians by directing his first efforts upon the north frontier.
 

With disconcerting speed, Napoleon was at Laon on the 12th of June, at Avesnes on the 13th, at Beaumont on the 14th and on the 15th at 3 o'clock in the morning his vanguard crossed the boundary on three different spots and marched toward Charleroi.

At that moment, the Allies did not expect any hostilities before the end of the month, and even proposed amongst themselves to take the offensive. Wellington was at Brussels, his cantonments were scattered about at Lens, Audenaerde, Alost, Ath, Ghent, Mons, Soignies, Genappe, Braine-le-Comte, Enghien, Ninove.

Blücher was at Namur with his camps at Marchienne, Fleurus, Moustier, Charleroi, Sombreffe and Gembloux.
 

On the 15th the French vanguards drive on the enemy from Gosselies and from Frasnes. The next morning Wellington hastens to Brussels to converse with Blücher near Ligny, whilst the general Gérard attacks the latter locality and takes it after a terrible fight; Vandam chases the Prussians from St-Amand and the army of Reille marches to Qautre-Bras.

So the Allies are forced to give up every idea of an immediate meeting.

Blücher is repulsed to the east followed up by marshall Grouchy and Wellington is forced to retreat to Mont-St-Jean (Waterloo). There it is where he was going to wait for the shock of Napoleon: he has already seen the opportunity of a favourable retreat by the proximity of the great forest of Soignes and of a new concentration at the other side of the Escaut (Scheldt), but he hopes to be able to be rejoined by Blücher in order to prevent the French army from marching to Brussels.

On his side, Bonaparte has not lost his time and the 17th after having chased near Quatre-Bras the last squadrons of the English cavalry he camps opposite Mont-St-Jean (Waterloo).