The organizational form of the army under the Ritsuryo system had an open senior officer and subordinate relationship while 'bushidan' was the group of people called 'tsuwamono' that served privately in the Heian period or was the combination of such groups.
律令体制下の軍団での組織形態は、国家の組織の中での公な上官と部下であるに対し、「武士団」は平安時代に「兵（つわもの）」と呼ばれるた者達が私的に従える集団、またはその集団の結合体である。