The ninja were very competent hand-to-hand fighters. They were trained from birth to fight with their hands and feet. They knew where and how to hit to paralyse or even kill when needed.
One reason that their style of fighting (Tai-jutsu) was so effective, was that they not only studied punching and kicking, but they studied the human body as well. Learning all about the weaknesses and strengths.
For example, punching a man in the face can be painful, but it might just piss him off, whereas a punch to the throat will be much more devastating.
Grappling was a strong part of the ninjas fighting technique. Along with bone-crunching kicks and punches, the ninja were equally as strong fighting from the ground.
When on the ground grappling, it is not likely that a punch or kick could be used effectively, so techniques such as arm bars and joint locks were used. The grappling was very similar to today’s judo or jui-jitsu.
A ninja studies the art of Taijutsu or “body movement”. Taijutsu doesn’t teach rigid and fixed methods like almost every other martial art does. Instead, it stresses fluidity, natural movement and spontaneity.
Also, the ninja learned to exploit the joints and pressure points of an enemy. When a punch or kick was thrown, a ninja wouldn’t simply block the attack, he would strike a pressure point or nerve center to cause the limb to lose its function.
Not only did the ninja learn to disable a person, he also learned to quickly and effectively kill. It is true that a ninja could kill with one blow by exploiting the weaknesses of the body.
Another important aspect of Taijutsu was learning to reverse any situation or attack. They were trained from childhood to be extremely flexible and could therefore escape any hold or lock they might be put in. They even played games as children where they were tied up and the object of the game was to get yourself untied as quickly as possible; within a few years, a ninja learned to get out of any type of binding.