These changes are always really, really interesting. One of my favorite moments similar to this is the Battle of Nicopolis [1] between the Ottomans led by Bayezid I and a Crusader force which included many Western cavalry forces. The much more mobile and easy-moving Ottomans were no match for the Western (especially French) forces who were accustomed with using their heavy armor during battle:
> The French knights thus continued up the hill, though accounts state that more than half were on foot by this point, either because they had been unhorsed by the lines of sharpened stakes or had dismounted to pull up stakes. Struggling in their heavy armor, they reached the plateau on the top of the slope, where they had expected to find fleeing Turkish forces, but instead found themselves facing a fresh corps of sipahis, whom Bayezid had kept in reserve. As the sipahis surged forward in the counterattack sounding trumpets, banging kettle drums and yelling "God is great!", the desperation of their situation was readily apparent to the French and some knights broke and fled back down the slope.