How long is a jo?

August 15, 2009

The defining characteristic of the jo staff is that it’s shorter than a bo staff, right? Traditionally, it’s four shaku, two sun, one bu (ancient Japanese measurements that work out to just over 50 inches). The modern “rule” is that it should come up to your armpit when you’re standing relaxed. But, why? What’s the meaning of this length?

According to legend, the jo was invented by Muso Gonnosuke Katsuyoshi after he lost a duel with Miyomoto Musashi using a bokken. Humiliated over his defeat, he retreated to a shrine on Mount Homan, in Chikuzen province, and meditated for 37 days. Finally, he was granted a divine vision (it’s amazing how many of the Japanese martial traditions come from divine visions – the gods there must be really interested in advancing the martial state of the art), inspiring him to create a short staff. With this, and techniques that he invented, he challenged Musashi to a rematch and won it – supposedly the only time that Musashi was ever defeated in a duel. The legends never explain how he chose four shaku, two sun, one bu as the proper length for the staff. It seems to be an arbitrary number. So, why is the jo the length that it is?

The jo is as short as it can be, while still being definitely longer than a sword. That’s the answer – the jo is long enough to outreach a sword. Remember that Gonnosuke was intending to win a duel against Musashi, who was famous for sword technique. He knew he’d be facing a sword, and he wanted to be able to stay outside its reach, but he needed to be able to move and shift as quickly as possible in order to defeat Musashi’s legendary (literally) technique.

In my school of swordsmanship, the Suisha Ryu, the primary focus of jo technique (and, for that matter, bo and yari technique as well) is on defeating a swordsman, and the jo is extremely well-suited to this task. It can strike from outside the sword’s range, and when the sword intercepts one end, the other end can immediately strike again from another angle. It’s extremely difficult for the swordsman to track both ends of the staff. Unlike the bo or yari, the swordsman can’t get inside the jo’s range, since the minimum effective range of the jo is actually shorter than the minimum effective range of the sword (at least, until you start bringing reverse-grip into the picture, but that’s material for another post).


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