Editing Battle of Ligny (section)

===Prussian retreat===
Sources differ over Gneisenau's leadership while Blücher was incapacitated. Chesney credits him with the decision to retreat north in support of Wellington: "Gneisenau, coming into temporary command after the fall of Blucher at the end of the battle, and finding the struggle for the present hopelessly decided, chose at all risk of inconvenience to abstain from the notion of a retreat to the east, and to keep as near as might be to the English army." [Chesney 1869, pp142–143]. Glover also writes "A retreat on Gembloux by the entire army would be the obvious course of action, except that this would lead to a complete break of contact with Wellington. Gneisenau therefore initially ordered a retreat directly north on Tilly, which would maintain that contact".{{sfn|Glover|2014|p=89}}   However, Parkinson, citing Prussian records, claims Gneisenau "raged" over the lack of British support at Ligny and decided to retreat east after Tilly: "And slowly, fatefully, Gneisenau's choice of retreat route swung towards Liege - abandoning Wellington to face Napoleon alone, outnumbered." [pp.&nbsp;228–9] Blücher later summoned his British liaison officer, Sir Harry Hardinge, to inform him: "Gneisenau has given in. We are going to join the Duke." [Parkinson p.&nbsp;232]. "This decision by Blücher is unquestionably worthy of the highest praise. Ignoring all the false courses of action that traditional practices and misplaced prudence might have suggested in such a case, he followed his common sense and decided to turn toward Wellington on the 18th, preferring to abandon his own line of communications rather than adopt half-measures. The battle he had lost had not been a rout. It had reduced the size of his force by only about one-sixth, and with nearly 100,000 men he could undoubtedly turn the battle that the Duke of Wellington was confronting into a victory".{{sfn|Clausewitz|2010|loc=Chapter 37}} It is noteworthy that when Blücher was found alive, he refused to consider resigning his command on account of his injuries, declaring he would rather have himself "tied to a horse than resign". [Parkinson p.&nbsp;229].

At about 22:00 the order to fall back was given. On the Prussian right, Lieutenant-General Zieten's I Corps retreated slowly with most of its artillery, leaving a rear-guard close to Brye to slow any French pursuit. Pirch I's II Corps followed the I Corps off the battlefield. They formed up again within a quarter of a league of the field of battle (about 3/4 of a mile), and retired to Wavre via Tilly, free of French pursuit. "Our infantry, posted behind Ligny, though forced to retreat, did not suffer itself to be discouraged … Formed in masses, it coolly repulsed all the attacks of the cavalry, and retreated in good order upon the height, whence it continued its retrograde movement upon Tilly. … At the distance of a quarter of a league from the field of battle, the army formed again. The enemy did not venture to pursue it. The village of Brie remained in our possession during the night, as well as Sombref, where General Thielemann had fought with the 3rd Corps".{{sfn|Mueffling|1833|p=74}} "At 10 o’clock the order to fall back was given, and the centre and right retrograded in perfect order. Forming again within a quarter of a league of the field of battle, they recommenced their retreat; and, unmolested by the enemy, retired upon Wavre".{{sfn|Maxwell|1833|p=213}}

On the left, Lieutenant-General Thielemann's largely-unharmed III Corps withdrew last with the army's various parks in tow, toward Gembloux where Bulow waited with the newly arrived IV Corps. He left a strong rear-guard at [[Sombreffe]]. "[Gneisenau], having undertaken the direction of affairs, ordered the retreat of the First and II Corps upon Tilly, and despatched Colonel Thile with directions to Thielemann, that if he could not effect a direct retreat upon Tilly, he was to retire upon Gembloux, there to unite with Bulow, and then effect a junction with the rest of the army".{{sfn|Siborne|1848|p=251}}

The village of Brye remained in Prussian possession (I Corps) during the night, as well as Sombref, where the III Corps had held Grouchy all day. The bulk of the rear-guards held their positions until about midnight. The final units of Zieten's I Corps rear-guard only left the battlefield at daybreak on 17 June, as the exhausted French failed to press on.{{sfn|Chesney|1907|p=136}} The last of III Corps was moved in the morning of 17 June completely ignored.{{sfn|Chesney|1907|p=136}}

[[Friedrich Wilhelm Freiherr von Bülow|Von Bülow's]] IV Corps, which had not been engaged at Ligny, moved to a location south of Wavre and set up a strong position on which the other elements of the Prussian army could reassemble.{{sfn|Chesney|1907|p=136}} Blücher was already in communication with Wellington. "The Field Marshall promised to come with his whole army; he even proposed, in case Napoleon should not attack, that the Allies themselves, with their whole united force, should attack him the next day. This may serve to show how little the battle of the 16th had disorganised the Prussian army, or weakened its moral strength".{{sfn|Mueffling|1833|p=77}}

{{Blockquote|Under the circumstances, the overall results of Ligny cannot appear out of the ordinary. It is a battle which 78,000 men lost to 75,000 by very slight tipping of the scales, after a long struggle, and without any truly glorious results for the victor, since his trophies consisted of only 21 guns and perhaps a few thousand prisoners.|Carl von Clausewitz.{{sfn|Clausewitz|2010|loc=Chapter 33}} }}

8,000 troops fled to Liege and [[Aix-la-Chapelle]]. These were mainly new draftees from the [[Grand Duchy of the Lower Rhine|Rhenish]] and [[Province of Westphalia|Westphalian]] provinces, and the [[Province of Jülich-Cleves-Berg|Duchy of Berg]]. Some of the [[Rhine]] provinces had previously been a part of France, and their contingents included old French soldiers.{{sfn|Siborne|1848|p=305}}