The present study aimed to clarify the inception and development of Kenji Tomiki's technical theory of budo during the pre-war Showa era, focusing particularly on the succession of Jigoro Kano's concept of judo as a martial art. The main points are summarized as follows:<br>  A letter written by Tomiki in 1928 reveals that he was interested in the comprehensive combat techniques of Ueshiba's aikijujutsu including the use of bare hands and weapons. Tomiki considered that devotees of budo should practice a comprehensive range of techniques from bare-handed combat to the use of weapons. While he mainly succeeded to shobu (martial arts) under the systematic judo theory of Kano, he also thought it possible to overcome the problems inherent to taiiku (physical education), shushin (development of the spirit), and ishinho (methods to ease the spirit) by studying aikijujutsu. The starting point of Tomiki's theory was to emphasize the kata training that simulated various situations in actual combat.<br>  During the prewar period, Tomiki tried to ascertain the fundamental principles of ken-no-ki (ki of the Japanese sword) and ju-no-ri (the principle of flexibility). These principles made it possible to complement the principle of judo as seiryoku-zenyo (most efficient use of energy) that Kano had proposed technically.<br>  In 1942, Tomiki published a research article entitled &ldquo;The systematic study of techniques while maintaining distance in judo: The principles of judo and the techniques of Aiki-Budo&rdquo;. In the article, he tried to present consistency between randori and these techniques while maintaining distance in judo, then established 6 fundamental laws of martial arts, including kendo, a system for education in these techniques, and the 12 basic kata.<br>  The consistent points of Tomiki's theory of budo in the pre-war era were to understand the strong and weak points of each competitive budo and kata, and the importance of kata. Although the emphasis on atemi-waza in Tomiki's theory had points in common with the combative techniques of school budo during the interwar period, Tomiki was really interested in overcoming the disadvantages of judo for sport based on Kano's concept of judo as a martial art. Tomiki mainly inherited the latter, and criticized competitive judo.<br>