While it is impossible to show the hammer principle in still photos, the following photos will give you some idea of the technique.
Bob Bremer measures off against Jim Sewell.
Dropping the hammer. This is done at the same time as the next photo.
The hammer principle is one of the best techniques that Bruce Lee taught. According to his lesson plans, which are published in volume 3 of Bruce Lee’s notes entitled Jeet Kune Do edited by John Little, it was also one of the first things that he taught. Bob Bremer seems to be the only one of Bruce Lee’s students who seems to remember it and teach it. He has been kind enough to share the finer points of the excellent technique.
The hammer principle is so great a technique that we spend part of each Wednesday night’s class working on it. After 3 years of working on it we have all come to the conclusion that we will never master it. This will become clear if I explain how we work on this technique.
First of all everybody gets a partner. The one doing the hammer principle measures off around 2 feet from his extended arm away from his partner who is taking on the role of trainer. He then attacks with a finger jab to the trainer’s forehead while dropping his arm as if he had a hammer in it. The trainer then tries to block the attack; the first thing we discovered was the major benefit seems to go to the trainer. It seems that more the man attacks; the easier it seems for the trainer to block it. The reason for this is that the trainer starts to pick up the attacker’s preparation. At first it will be an obvious preparation. For example, he’ll move his body first and then his hand, instead of hand first. The reason the blocker is called the trainer is that his job is to start pointing out the attacker’s preparation. At first he’ll only notice large body motions like dropping or raising the body a split second before the attack.
Once he rids his partner of these larger motions, he seems to be able to notice more subtle preparations. He may notice that the attacker’s elbow comes out first, or he may notice a slight facial expression before the attack. Once he points this out, and the attacker has gotten rid of all physical preparation, the trainer seems to be able to sense when the attack will occur. He will start to perceive the attacker’s physical tension, which will occur a split second before he attacks. Once the attacker has learned to hide his physical tension, he may be able to then work on what Bruce Lee called non-intention. This is the difficult stage where "you don’t hit. It hits". I’ve only been able to achieve this a couple of times. It is a very strange feeling to suddenly strike out with an attack, and not realize until afterward that you hit. When you are able to hit with the hammer principle without intention, it is impossible for the trainer to block you. If you strike without any preparation and without intention, your hit will land before it is seen.
If you practice the hammer principle for a long time, a special benefit will occur. The attacker will be able to notice when the defender/trainer’s concentration wavers. Bruce Lee told Bob Bremer that when he did the hammer principle on him he (Bruce) seemed to know when Bob lost his focus. As soon as Bruce noticed Bob’s focus waver, he would smack Bob hard on the forehead from about 3 feet away. Bruce Lee told Bob that at some point there would be a split second when his opponent was not with him. He said that he always seemed to know when that was.
In our Wednesday Night JFJKD class we even make it more difficult to master the hammer principle by switching partners. The advantage of this is that the trainer gets to analyze every member of the class for their preparation. By doing that, we have found that when sparring it becomes much easier to recognize an attack and therefore to intercept it.
Finally if the person attacking becomes too successful from 2 feet away, then we move him to 2 and half feet away. If you keep making it more and more difficult for the student, he will continue to keep growing and growing as a martial artist.