The 4th (Bulow’s) corps, which, up to this time, had not fired a shot in the campaign, set out at sunrise on the 18th towards the French right flank, by way of St.-Lambert; they were preceded by strong patrols to ascertain whether Napoleon had yet taken precautionary measures to obstruct their junction with us, or to protect his own right. It was soon discovered that this precaution, so essential to the protection of his right, had been overlooked by the Emperor: the Prussians immediately availed themselves of the advantage which his neglect afforded, by throwing a force into the wood of Paris, which commanded the defiles of the Lasne and St.-Lambert. Zieten’s, or the first corps, was to march, by Fromont and Ohain, direct upon our left; Pirch’s, or the second corps, was to follow Bulow’s: they were delayed by a part of Wavre being on fire, and by the great difficulty of making progress through the defiles of St.-Lambert. They were expected, nevertheless, to be up by or before two o’clock. It was near five o’clock when the first two brigades of Bulow’s corps debouched from their covered position in the wood of Paris. The 15th brigade, under general Losthin, and the 16th under colonel Hiller, with some cavalry, (altogether about 16,000 men and forty-four guns,) drew up perpendicularly to the French right flank; upon which Durutte’s division, which formed the right of the French main front line, was thrown back _en potence_. The Prussian commanders detached some battalions to Frischermont and Smohain to secure their right flank, they also sent a few battalions to the Lasne, the woods of Virère and Hubremont, to support their left. So stealthily and cautiously did the Prussians approach Smohain, that both the enemy and allies seemed astounded upon their debouching from the enclosures. General Domont’s cavalry were still _en potence_, but at a considerable distance from the Prussians, whose advanced batteries opened upon the French cavalry, although at a long range; but this was merely to acquaint Wellington and Napoleon of their arrival, which doubtless alarmed the latter, whilst, by the former, it was listened to with joy.