The majority of martial arts have specific techniques that are trained to be used against specific attacks. For example, against a wide right punch a practitioner may be taught to block with an outward sweeping motion of the left arm, followed by or combined with an offensive movement. Against a low knife thrust, a practitioner may be taught to use a downward X block. Although the above defensive examples could work, there are a number of problems with the underlying concept, which will cause this type of response to fail in a significant number of cases.
First, the initial motion of attack may be a fake. Using the first example above, the attacker could fake a wide right and strike with a straight left. Because the practitioner's defense is dependant on the particular strike the defense is based on, it will likely fail. If the attacker uses a quick right fake, drawing a particular block, he can then strike the opening created by the blocking motion.
Second, the initial motion may be misjudged. The average person doesn't throw a perfect straight shot or an extreme wide and horizontal hook. If a practitioner thinks a straight right is on its way, and reacts with a movement specifically designed for the straight right, but the opponent has actually thrown a hooking punch, the strike may slip around the block and strike the practitioner.
Aside from the initial motion being faked or misjudged, the attacker may be able to exploit the openings created by this specific type of blocking. A number of techniques in less mainstream martial arts were created to take advantage of particular blocking motions that are taught in most styles.
For the reasons above, and others, training to match specific defensive techniques to specific attacks is most likely not the best use of time. Because an initial motion may be a fake, and because the path and destination of the motion is unknown, there is a more effective way to respond. This is based on what we call zone theory.
Every attack is initiated from a particular location and is aimed at a particular location. We call these two locations initiation zones and contact zones . The factor that determines the path that an attack must travel, the angle of initiation, from an initiation zone to a contact zone is the relative position of the participants. If your opponent is standing directly in front of you with his and your feet parallel, both of you can strike directly forward and hit each other. If your opponent is standing with his left foot forward, and you are standing to his left, with your right foot forward, you can strike him directly, but he cannot strike you without turning and/or moving his feet.
The opponent's angles of initiation can be changed by manipulating relative position, or by jamming and disrupting his striking tools. The contact zones he can strike can also be changed by relative position and/or by an effective physical cover. If you can manipulate the relative position, limiting the opponent's angles of initiation and contact zones, and cover the remaining areas that are left open, the opponent will be unable to strike you effectively. If the opponent is not aware of and/or unable to protect his open contact zones and cannot disrupt your angles of initiation, you will be able to attack him while he is unable to attack you. If your offensive and defensive methods are based on the above zone theory, your chances of success will be far greater.