While the Knights of the Teutonic Order formed a thin ruling class by themselves, they have extensively used mercenaries, mostly German, from the Holy Roman Empire, to whom they granted lands in return. This gradually created a new class of landed nobility. Due to several factors, among which was the high rate of early death in battle, these lands became concentrated over time in the hands of a relatively small number of noblemen each having a vast estate. This nobility would evolve to what is known as the Prussian Junker nobility.