"Ninjitsu" consists of delivering Maximum force with minimum movement. Most attacks "disguise" the power in the movements. They are based upon an acute knowledge of the bodies circulatory and nervous system. The pressure points. A seemingly simple movement has the ability to incapacitate, cripple or kill the opponent with almost no visible force exerted at all. It is the art of "the stealth kill". Most ninjas didn't wear hoods and masks. Most ninjas looked like an average pedestrian a fisher man, a peasant, a drunk or merchant. They wanted to appear as "un-ninja like" as possible, hiding in plain sight and killing in an instant, with out the use of a weapon. The indicative hood and mask was for night missions and it was usually "blue" . Black was too dark and usually would stand out at night when the prevalent color of night is in fact "blue".
I recently began studying Wing Chun. One thing that is evident in the principals of Wing Chun is everything, everything Bruce Lee tried to convey was, in fact the principals of Wing Chun. Jeet Kun Do itself was "Bruce's" application of Wing Chun.
The name "Wing Chun" roughly translates to "stop fight" or "stopping the attack" How do you do that? By preempting an attack "intercepting" it if you will and thereby removing the opponents power by nipping it in the bud.
"Don't think Feel". The legendary quote from the beginning of E:tD, Bruce is talking about sensitivity training or "chi sao" or "sticking hands" where you should "feel" the movement of your opponent and react accordingly. "When the opponent contracts I expand, when he expands I contract and when there is an opening, I do not hit. It hits all by itself!" this an extension of this principal where it must be ingrained, not the technique, but the mindset the reflex.
Bruce's statements regarding the "futility of martial art styles" were based upon the limitations of Wing Chun movements, so when he moved to formulate Jeet Kun Do he expanded the range of movements to encompass more than just in close fighting. Wing Chun being primarily an upperbody martial art with only "two" kicks.
Wing Chun is an "internal form of martial arts Derived from Taoist principals each of its separate parts or movements are representations of the Bagua which represents heaven and earth and all elements in between. Your power comes from the inside and center line. when preparing to strike the palms should be facing up ward, the arm slightly twisted so that the elbows are resting on your rib cage, opposed to being parallel with your body.
To properly understand and utilize Jeet Kun Do, one must first have an understanding of the principals of Wing Chun. To be "formless, shapeless. like water" is a reference to having no particular way of engaging an attacker/ opponent. Meaning you should not focus on "how" but rather "where" and "when" wheather it is a "punch" an "elbow" or "palm strike". You simply get your extremity, your "weapon" to the target in the fastest most "effectively damaging" way possible. For some that may be a palm for others it may be a fist. It is simply a reiteration of "don't think, feel". What set Bruce apart was having a knowledge of "self". "Self" meaning his own personal abilities, His range his speed his power.
Put your arms out in front of you as far as they will stretch. and then extend them to your side in the same way. now do the same wit your legs even if you aren't that flexible. This is your range this is your "circle". Get to know it well and master it, as it is an "extension" of yourself. When one learned the circumference of "their circle", when on has explored all variables that can occur within that space, then you will be truly formidable.