In Japan many people used a short staff, also known as the jo. It is similar to the staff used by priests and monks. The jo is a wooden staff with a diameter of approximately 1.91 cm (3/4") and a length of 127.5 cm (4'.3"). There exists a similar weapon called the bo but, the bo is much longer and not a part of normal Aikido training.

The jo is a very flexible weapon and can be used to approximate the movements of the sword (strikes and sweeps), the naginata (like a halberd, a lance with a type of short sword at its tip) and the lance used in a stabbing motion. The jo is a very useful weapon.

In general, the katana is used in direct cutting and slashing movements. The jo, however, moves in a more circular type of movement. The study of the jo goes hand-in-hand with the study of the katana. Additionally, the use of the jo can be instrumental in the development of physical flexibility. Regarding traditional arms, the jo is the only weapon that can prevail against the katana. The reason for this is that the jo is made from Japanese white oak or biwa (the kumquat tree) which is hard yet flexible making it very difficult to cut.

The jo is also of great interest because it was used by the Japanese priest Takuan to overcome an attack by Miyamoto Musashi (arguably the most famous swordsman of Japan.) Musashi was so impressed by his defeat and the ability of the priest that he immediately began a study of the use of the jo. The study of the jo can be useful in understanding the strategy of the katana and in the study of Aikido. Presently, the study of the jo is a requirement of the Japanese Federation of Kendo along with the study of Iaido.