older lotr illustrations sometimes depict éowyn wearing ridiculously small armour. apart from the problem general sexualisation of the only female character (who really does anything), there’s another hilarious thought:
éowyn pretended to be dernhelm, a man. to fit in, she must have worn men’s armor. so the armor in the illustrations is normal for rohirrim.
therefore, all the rohirrim rode to war just like that: