Iaido schools taught distance and timing with two-man kata using bokken . A bokken though is a weapon in its own right and is too dangerous for a mock fight. The solution to this problem was the development of armor and bamboo weapons. The armor is based on battlefield armor. The shinai is a bundle of bamboo strips tied togather.
Further safety is provided by the rules of contest.
Cuts and thrusts are only allowed to specific areas. Even then, they only score points if the judges are satisfied with the quality and sincerity of the attack. Kendo has long been taught in Japanese schools and is hugely popular there. Compared to most martial arts, it is expensive to take up because of the equiptment. This means that its international spread is quite slow.