How did the arrival of Prussian troops affect the Battle of Waterloo?

The arrival of Prussian troops was a decisive factor in the Battle of Waterloo, ultimately turning the tide in favor of the Allied forces.1

Throughout the day, the Prussian army under Gebhard Leberecht von Blücher exerted increasing pressure on Napoleon’s eastern flank. This intervention forced Napoleon to divert significant resources—including a corps under the count de Lobau and several battalions of the Imperial Guard—away from his primary assault on the Duke of Wellington’s center to prevent the Prussians from advancing into his rear.12

Napoleon’s delay in starting the battle until midday, intended to allow the ground to dry, provided the Prussians with the necessary time to reach the battlefield. By the final stages of the engagement, the arrival of a Prussian corps under Hans Ernst Karl von Zieten helped Wellington reorganize his defenses. Following the repulse of the French Imperial Guard at 8:00 pm, a general Allied advance combined with further Prussian attacks threw the French army into a panic, leading to a disorganized retreat and the final defeat of Napoleon.12