Kendo is a type of athletic contest in which practitioners wear kendo-gu (protective armor) and use shinai (bamboo swords) to strike each other.
However, kendo is a budo (martial way) that aims to forge the mind and body of practitioners and facilitate the development of character through continued keiko (practice).
As of March 2017 there are 1,853,553 registered kendo dan grade holders (in Japan), of whom 543,921 are women.
Iaido is derived from methods of using the nihonto (Japanese sword) that emerged in the Muromachi period (1333–1573). The object of iaido is to learn to draw the sword in an instant to overcome an aggressor. It is a “Way” in which practitioners seek to train the mind and body through developing a spiritual appreciation of the relationship between life and death, movement and stillness.
The connection to kendo is very close, and it is said that iaido and kendo are two sides of the same coin.
As of March 2017 there are 93,166 registered iaido dan grade holders (in Japan), of whom 12,201 are women.