By Greg LeBlanc 
Wing Chun at its core follows a particular tactic that defines the logic of its training methods and especially the rationale for becoming expert at the reflex drill Wing Chun has become famous for called Chi Sau. Without understanding the design of Wing Chun, Chi Sau will not make sense. As a drill it only has a direct relationship to self-protection if and when at close range the punching line angles have been blocked, tangled or jammed. In essence Wing Chun capitalizes on a particular tactic called Jeet; Jeet refers to the interception of an attack with an attack. In an ideal form the Wing Chun practitioner will advance as the attacker advances, intercepting the offending attack with a defending attack, all done in one step. Arms and hands form a barrier and bring the attack tools closer to the target, sharpening the response timing and using the closest attack tool to the primary target (the General). 

If the primary distance is lost or given up (such as by stepping back), the Wing Chun defender cannot continue using his or her main tactic. If the bent arm range is lost by stepping back or not maintaining proper range with the target, the kicking and grappling ranges open up and all is lost in terms of what Wing Chun seeks to attain and preserve as a range and the chief target access. The guidelines are to attain the proper range, to retain the proper range and to maintain pressure towards the center-line of the target at all times. The range that Wing Chun specializes in is meant to last only a few seconds, providing a clear path to the primary target and redefining that path if momentarily blocked out or obstructed.

The function of Chi Sau and the helping/assistant hands it develops is to build into muscle memory to always being chasing the center of mass and to change to a new angle of attack if required. All other benefits are by-products of proper training and fringe benefits of understanding the logic and function of the drill. To train complicated usage and near magical definitions of what is possible is IMHO to train in what I refer to as the Chi Sau bubble. To not understand the true timing of interception in one step, to not train the hands for close range full power impact and to not train at a distance from live and common attacks, is also to train in a Chi Sau bubble. This idea of application is different from the moving range of symmetrical fighting (competitive style) is in concept different from the asymmetrical event of a random self-protection problem or to be suddenly and with out warning preyed upon. In the later event very little preparation is possible and options for response are best kept simple, direct and efficient. The other missing element I would add is that often the golden moment of deescalation is present and should proceed if possible any response that requires Wing Chun skills. To quote Sun Tzu “The supreme art of war is to subdue the enemy without fighting.” 

By Greg LeBlanc
The function of the Chi Sau drill is to build automatic reactions at close range. In the application of Wing Chun the advancing attacker is met using the primary preemptive tactic called Jeet. If your attack becomes obstructed, Chi Sau skills take over. The drill is training us to skillfully react from being tangled up. In thinking about what we are preparing for, the attacker on the street is not going to hit in a predictable manner, but will be a moving target either to you or moving away from you, may very likely land hits on you, and will be hitting in combinations (skilled or wild). If Chi Sau trains us for something else than the above, then that training becomes more about the drill and less about what the drill is preparing us for. Meaning it is possible to become very skilled at the Chi Sau game, but only under conditions that take place in the drill itself (sometimes called the Chi Sau bubble). Chi Sau is a drill intended for training at the elbow range (where an obstruction takes place), if we break the distance of the drill (leaving the elbow range) then we have effectively ended the drill.
If we step out the the Chi Sau/Gwoh Sau drill we are now are playing at San Sau range (distance fighting range); this distinction is something I try and make very clear when I am coaching. The application being, if someone wants to Chi Sau/Gwoh Sau but then jumps out of the elbow range, I know that the play has now switched to San Sau. One option I employ for clarification is to use the Predator Armor, which allows for a safe way to test the above statements. To see if in fact a live attacker can be intercepted (regardless of the types of attack), hit with accurate and full power punches, skillfully using assistant hands as needed and all done in a way that doesn't easily allow for retreat or the trading of punches. If Wing Chun doesn't meet an attack with an intercepting attack, if it doesn't take position and control centerline; what then is the meaning of the Chi Sau drill? In other words Chi Sau as the soul of the system is outlining and defining the way Wing Chun was designed to be used. If we are not taking position and attacking the attack, but instead are moving in and out (stepping back), how does Wing Chun then differ from any other punching system? 

By Greg LeBlanc
Any martial art I have studied eventually gave the same advice for application, that you have to pick a few techniques and train them until they are pure instinct. Most traditional martial art systems preserved more actions than what is needed for self-protection, they are safeguarding the history of that system and how it developed over hundreds of years. The fact is only a few actions can be really trained into muscle memory that will function under pressure in an adrenalized state. The other point to be made is that to become truly proficient at any action it needs to be practiced thousands of times, eventually the punch you thought you knew becomes something else. Kung Fu means to do something many times until you can do it without thought or hesitation. In this line of thinking the most simple, direct and efficient actions are not only the faster road to this goal, but also tend to be the hardest to deal with by anyone who does not practice this same approach. Wing Chun starts here. It's development was based on the experience of seasoned Chinese martial artist who pooled their collective know-how into what was considered most essential, all things being equal. Wing Chun is simple by design, anything other than this and it loses what makes it a significant counter to other approaches that are less direct or more complex. The training is much more about the attributes, concepts and qualities of balance, position, speed, power, mobility, structure and accuracy than learning so-called techniques. The true technique of Wing Chun is to preempt any aggression with a uniform response that intercepts, bypasses and dominates position and center of mass. Using this method properly offers the fastest response under pressure from a situation that lacks preparation and is unprovoked. Rather than prolonging an altercation which can increase the danger and fatigue of the fight with each second, Wing Chun is focused on how to quickly end the fight. To this end it takes the fight back to the aggressor, it switches the relationship of who is attacking who, it trains to attack the attack; or as my teacher would say “to go inside the house to fight the fire.”