Ever since the dwarves entered the family of nations, their warriors have been feared for their mighty weapons and armor, and their still mightier strength which shatters the strongest dwarven plate.
Pity it’s a crock.
You see, shortly after the dwarves started trading with other races, it became clear that their customers’ hunger for high-quality armaments was inexhaustible. This worried the Forgemasters, who felt, in a typically dwarven and clannish way, that it was perhaps not the best idea to equip a world full of dangerous non-dwarves with the best dwarvenkind had, no matter how well they paid.
Thus, all dwarven armor and weaponry made for external sale has a minor but fatal flaw concealed somewhere in the manufacture. Dwarven warriors are trained in the locations of these weak spots, which allows them to shear off blades and smash plate mail to shards when they hit the sweet spot juuuust right.
For a while, human knockoffs were a concern to them, but it appears that human smiths have taken to slavishly imitation of dwarven craftsmanship, including the flaws. Clearly, brains are in the beard.