Editing Battle of Waterloo (section)

===Zieten's flank march===
[[File:Battle of Waterloo map.jpg|thumb|upright=1.35|Situation from 17:30 to 20:00]]
Throughout the late afternoon, the [[Order of battle of the Waterloo campaign#Prussian I Corps|Prussian I Corps]] (Zieten's) had been arriving in greater strength in the area just north of La Haie. General [[Karl Freiherr von Müffling|Müffling]], the Prussian liaison to Wellington, rode to meet Zieten.{{sfn|Hofschröer|1999|p=125}}

Zieten had by this time brought up the [[Order of battle of the Waterloo campaign#Prussian 1st Brigade|Prussian 1st Brigade]] ([[Karl Friedrich Franciscus von Steinmetz|Steinmetz]]'s), but had become concerned at the sight of stragglers and casualties from the Nassau units on Wellington's left and from the Prussian 15th Brigade (Laurens'). These troops appeared to be withdrawing and Zieten, fearing that his own troops would be caught up in a general retreat, was starting to move away from Wellington's flank and towards the Prussian main body near Plancenoit. Zieten had also received a direct order from Blücher to support Bülow, which Zieten obeyed, starting to march to Bülow's aid.{{sfn|Hofschröer|1999|p=125}}

Müffling saw this movement away and persuaded Zieten to support Wellington's left flank.{{sfn|Hofschröer|1999|p=125}} Müffling warned Zieten that "The battle is lost if the corps does not keep on the move and immediately support the English army."{{sfn|Uffindell|Corum|2002|p=232}} Zieten resumed his march to support Wellington directly, and the arrival of his troops allowed Wellington to reinforce his crumbling centre by moving cavalry from his left.{{sfn|Hofschröer|1999|p=125}}

The French were expecting Grouchy to march to their support from Wavre, and when Prussian I Corps (Zieten's) appeared at Waterloo instead of Grouchy, "the shock of disillusionment shattered French morale" and "the sight of Zieten's arrival caused turmoil to rage in Napoleon's army".{{sfn|Uffindell|Corum|2002|p=233}} I Corps proceeded to attack the French troops before Papelotte and by 19:30 the French position was bent into a rough horseshoe shape. The ends of the line were now based on Hougoumont on the left, Plancenoit on the right, and the centre on La Haie.{{sfn|Hofschröer|1999|p=139}}

Durutte had taken the positions of La Haie and Papelotte in a series of attacks,{{sfn|Hofschröer|1999|p=139}} but now retreated behind Smohain without opposing the Prussian 24th Regiment (Laurens') as it retook both. The 24th advanced against the new French position, was repulsed, and returned to the attack supported by Silesian ''Schützen'' (riflemen) and the F/1st ''Landwehr''.{{sfn|Hofschröer|1999|p=140}} The French initially fell back before the renewed assault, but now began seriously to contest ground, attempting to regain Smohain and hold on to the ridgeline and the last few houses of Papelotte.{{sfn|Hofschröer|1999|p=140}}

The Prussian 24th Regiment linked up with a Highlander battalion on its far right and along with the [[Order of battle of the Waterloo campaign#Prussian 4th Brigade|13th ''Landwehr'' Regiment]] and cavalry support threw the French out of these positions. Further attacks by the 13th ''Landwehr'' and the 15th Brigade drove the French from Frichermont.{{sfn|Hofschröer|1999|p=141}} Durutte's division, finding itself about to be charged by massed squadrons of Zieten's I Corps cavalry reserve, retreated from the battlefield. The rest of d'Erlon's I Corps also broke and fled in panic, while to the west the French Middle Guard were assaulting Wellington's centre.{{sfn|Uffindell|Corum|2002|pp=232–233}}{{sfn|Chesney|1874|pp=187–190}} The Prussian I Corps then advanced towards the Brussels road, the only line of retreat available to the French.