Panther tank
It was in France that the allies first began to face the German Panther tank. The superior frontal armor of this tank, along with the Tiger I, Tiger II, and newer "Panzerjägers", made the 75mm armed US tanks and tank destroyers less effective. The presence of these German tanks expedited the development and production of US armored vehicles armed with 90mm guns - the first to be introduced being the M36 tank destroyer.