As someone who plays SvN quite often, I can draw one conclusion: Nords are nothing short of freaking brutal. They demolish any Swadian army of the same size that does not have more than 30-40% in cavalry. Suffice to say, a single "Kingdom of Nord has declared war on Kingdom of Swadia" line is often enough to ruin my day.
(Then again, I mostly play Swadia without any cavalry, so my only anti-Nord defense is sergeants-and-shots, the former falling too far behind Nords in competence to be reliable. It is also possible that this is owing to an AI problem in Diplomacy - if you tick the "polearm fix" option, your sarge will keep trying to draw his awlpike in the middle of facehugging combat, to predictable result.)