Between Namur and Dinant, Grouchy had barricaded every narrow passage, and placed obstacles at intervals on the roads; and in this way hindered the chances of Prussian pursuit, and gaining time for himself.
The scattered remnants of Napoleon’s army were fleeing along the roads from Charleroi towards Avesnes, Laon, and Phillippeville. Grouchy therefore designed his retreat so as to bring his army clear of pursuit as quickly as possible, and to work his way towards the fragments which were with difficulty being collected round Laon by Soult, Reille, and others. He hoped to reach Paris before the allied armies, in time to organise a defence, or perhaps to effect a junction with the army of the Alps under Suchet and with Lecourbe. Napoleon himself had given up the plan of rallying his routed army under Grouchy’s still formidable force, and had ridden in haste to Paris, where his position was already precarious.
On the 21st, Grouchy marched from Dinant to Phillippeville, but Pirch I. did not pursue. His Corps was required elsewhere, to blockade some of the fortresses which barred the line of advance of Blucher’s army. Grouchy might have retired through Givet and down the valley of the Meuse, instead of risking the more dangerous road to Phillippeville. But his aim was to draw near to any body of troops which were left from Napoleon’s army, and to avoid marching down the narrow defile of the Meuse valley where he would be liable to an attack in flank or in rear, under great disadvantages. Zieten was at Beaumont on 20th June, 12 miles from Phillippeville, but he had marched at daybreak on the 21st. Pirch, marching to Thuin on the 21st, was moving parallel to Grouchy, but the latter’s march was not hindered.
Four French fortresses barred Blucher’s advance--Landrécies, Maubeuge, Avesnes and Rocroi. It was necessary to reduce these before any further advance on Paris was made; hence Grouchy was able to retreat unmolested for the greater part of his movement. On the 22nd he reached Rocroi; and Mezières on the 23rd. His force constituted an important menace to the left flank of the Prussian army; and Blucher was thus obliged to detach several parties of cavalry to watch the French movements.