Musashi

Experience was his Teacher

- Musashi engaged on duels both using wooden and real swords. The process for him to hone his skill in deadly combat requires him to self analyze, formulate strategies and understand the principle of combat. This allows him to survive these experiences perhaps by skill and luck. All his experience and understanding culminated to what he called Niten Ichiryu - his personal understanding. This happened during the times when dueling are common. Musashi style was tested and proven because he survived. I can't imagine learning his style or inventing a kenjutsu style just by reading the book ( Gorin no Sho). It is difficult to replicate this process

because the era of fighting with swords has long been over. You must have teacher to learn either kendo or kenjutsu. With a teacher to guide/coach, feedback, effective self reflection and assessment...maybe improvement is much easier.