Sumo began as a ceremonial religious ritual, but through the course of time, developed into a form of military training.

From as early as 719, by Imperial edict, the most skilled men in horse-racing, archery and sumo were ordered to be gathered from the provinces in order to partake in the courts most important ceremonies. Officials representing the Imperial guard were sent out to recruit these strong men from all corners of the country, and encouraged everyone to try for selection. Emperor Ninmyo (reigned 833 - 850) proclaimed in his first year of rule that "the wrestling festival is not only an occasion for mere amusement, but the most appropriate observance of the development of the military strength of the nation."(Hiroyama, 1940, pg 16)

By the close of the 10th century, the power and wealth of the Imperial court began to decline, bringing an end to the lavish feasts and extravagant performances for which sumo was famous. The popularity of sumo therefore declined, and the sport was adopted by the army as part of their training. In its early stages, sumo had been quite rough and violent, though during the Heian period, techniques had been refined, and proper rules established, making it suitable to be included in military training.

From 1156 to 1185, Japan was embroiled in a fierce civil war over the succesion of the Imperial line. Following the establishment of the first Shogunate in Kamakura from 1185 to 1392, sumo began to be practiced more and more as a martial art by the warrior classes. It is said that Minamoto-no-Yorimoto (reigned 1148 - 99) was an enthusiastic follower of sumo and encouraged its inclusion in military training.

In feudal Japan, warfare comprised mainly of encounters between individual warriors, so to have sumo skills was extremely advantageous. Sumo, archery, swordsmanship and the equestrian arts were the basic skills practiced for military training. Sumo was viewed as particularly important as an essential skill for mortal combat, as it allowed a warrior to to throw his opponent to the ground to kill or subdue him. Various new and more sophistiacated techniques were developed accordingly, in order to make it more effective during combat.

Feudal lords at the time encouraged the practice of military games such as archery competitions, equestrian contests and wrestling matches. In between battles, these sports were widely practiced by the samauri class, and were particularly popular with the ruling Shoguns of the time as a form of entertainment.

The Ashikaga period (1338 - 1568) was the period in which sumo was most widely practiced as a military art, as it was a period of almost incessant warfare. The major feudal lord of the 16th century, Oda Nobunaga held major tournaments at his castle, during which the ring mas marked out on the ground for the first time.

Fighting Lords engaging in wrestling