Shinichi SATO firmly stated in "A disturbance of Northern and Southern Courts" published in 1965 that bushi was 'the vocational individual or group that served the ruling class with martial arts.'
佐藤進一は1965年の『南北朝の動乱』の中で、武士を「武芸をもって支配階級に仕える職能人もしくは職能集団」と言い切る。