And then, in 1391, Yoshimitsu bent his efforts on creating divisions and strife within the very powerful Yamana clan, which held the role of shugo (de facto governor) for 11 provinces and were called "the lords of one-sixth of all Japan;" Yoshimitsu succeeded in bringing about the family's ruin when he had the brothers Tokihiro and Ujiyuki YAMANA strike against their own relatives, Ujikiyo and Mitsuyuki YAMANA.
そして、明徳2年（1391年）、11カ国の守護となり『六分の一殿』と呼ばれた大勢力の山名氏の分裂をけしかけ、山名時熙と山名氏幸の兄弟を一族の山名氏清と山名満幸に討たせて没落させた。