Some schools specifically emphasize their training in Jo (staff), Tanto (wooden knife) and Bokken (wooden sword) which are the three basic weapons in Aikido. However, since the main purpose of Aikido is not the use of weapons, trainees are required to attend at least two classes per week without weapons.
There are different reasons for the existence of weapons in the training of Aikido. Many of the moves in Aikido are based on classical weapon based martial arts. For example, all the strikes in Aikido come from the sword. This is the reason why the unarmed attacks in Aikido seem to be slow, ineffective and lacking force, especially for someone who has trained in arts like Karate and Boxing.
First of all, training with weapons help the trainee to develop proper mai’ ai (distance between two opponents). The constant moving into and out of a weapon’s range enhances the instinctive perception of time and distance. Those terms are very important in practicing without weapons.
Another important reason for training with weapons in Aikido is the existence of many advanced defense techniques against weapons. To ensure the safe execution of these techniques, it is important that the student knows how to properly attack using a weapon (uke) as well as how to defend when he/she in the opposite situation (nage).
Often, significant ideas behind the movements and techniques in Aikido are presented more effectively with the use of weapons. Also, practicing weapons kata helps the practitioner comprehend the general principles of movement in Aikido. Training with weapons offers a vigorous way of practicing Aikido, especially when training in unarmed defense against an armed attack.
Training with weapons provides the aikidoka with the opportunity to develop his/her reactivity and sensitivity to the movements and actions of the people surrounding him/her. Through weapons training, an aikidoka can easily be relieved from the mentality of being competitive because the emphasis and attention is being focused to his/her cognitive development.
Finally, weapons training is a good way to teach the principles behind the lines of attack and defense. All Aikido techniques start with the defender moving outside the line of attack in order to create a new line (which is usually never in a straight forward direction) and apply and Aikido Technique.