, was one of the earliest disciples of Kanō Jigorō

Kano Jigoro

was the founder of judo. Judo was the first Japanese martial art to gain widespread international recognition, and the first to become an official Olympic sport. Pedagogical innovations attributed to Kanō include the use of black and white belts, and the introduction of dan ranking to show the...

. Yokoyama was 22 when he entered the Kōdōkan

Kodokan

, or the Kodokan Institute, is the headquarters of the worldwide judo community. Literally, kō means "to lecture" or "to spread information," dō means "the way," and kan is "a public building or hall," together translating roughly as "a place for the study or promotion of the way." The Kodokan was...

 dojo in April, 1886. Yokoyama further assisted Kano in establishing the Kōdōkan

Kodokan

, or the Kodokan Institute, is the headquarters of the worldwide judo community. Literally, kō means "to lecture" or "to spread information," dō means "the way," and kan is "a public building or hall," together translating roughly as "a place for the study or promotion of the way." The Kodokan was...

. He was awarded the seventh grade in October, 1904, which was the highest dan in judo

Judo ranks and grades

In Judo, improvement and understanding of the art is denoted by a system of ranks split into kyū and dan grades. These are indicated with various systems of coloured belts, with the black belt indicating a practitioner who has attained a certain level of competence.-The Kōdōkan Kyū-Dan ranking...

 at the time. Yokoyama was considered the most formidable of all judo experts of his time, which reflected in his nickname of .

Four Guardians of the Kōdōkan

When Kanō Jigorō

Kano Jigoro

was the founder of judo. Judo was the first Japanese martial art to gain widespread international recognition, and the first to become an official Olympic sport. Pedagogical innovations attributed to Kanō include the use of black and white belts, and the introduction of dan ranking to show the...

 began developing judo from jujutsu

Jujutsu

Jujutsu , also known as jujitsu, ju-jitsu, or Japanese jiu-jitsu, is a Japanese martial art and a method of close combat for defeating an armed and armored opponent in which one uses no weapon, or only a short weapon....

, practitioners of jujutsu opposed his efforts. However, Kano drew a loyal following that included exceptional fighters. Hence the term "Four Guardians of the Kōdōkan

Kōdōkan Shitennō

Four Guardians of the Kōdōkan refers to the four notable judo competitors of the early Kōdōkan: Tsunejiro Tomita, Yamashita Yoshiaki, Yokoyama Sakujiro, and Saigō Shirō.- Four Guardians of the Kōdōkan :...

" came into existence referring to Yokoyama Sakujirō along with Yamashita Yoshiaki

Yamashita Yoshiaki

Yamashita Yoshitsugu , was the first person to have been awarded 10th degree red belt rank in Kodokan judo. He was also a pioneer of judo in the United States....

, Tsunejirō Tomita

Tsunejiro Tomita

, born , was the earliest disciple of judo. His name appears in the first line of the enrollment book of the Kōdōkan. Tomita, together with Saigō Shirō, became first in history of judo to be awarded black belt grade by the founder of judo Kanō Jigorō, who established the ranking system...

, and Saigō Shirō

Shiro Saigo

was one of the earliest disciples of Judo. Saigo, together with Tsunejiro Tomita, became first in history of judo to be awarded black belt grade by the founder of judo Jigoro Kano, who established the kyu-dan ranking system.-Biography:...

.