Krav Maga is designed to provide the most effective response for an individual across the whole range of situations in which one's safety is in danger. Here is a brief discussion on four key areas that I've picked up on in the time I have been training in krav maga. These are not exhaustive of the principles behind krav maga but do give a good overview of some important considerations that go into training:
1) Attack vulnerable areas of the body. Consider that when someone attacks you and you are able to fight back, any action that you take can be said to have an 'opportunity cost', that is the cost of the action you didn't take weighed up against the one you did. Given that when your life is in danger your aim is to survive it makes sense to ensure that your efforts in defending yourself are focused on inflicting as much damage on your attacker as possible so that they are neutralised and no longer a threat to you. As such krav maga encourages attacking the most vulnerable areas of the body. The groin strike for instance is a staple of many techniques as are eye gouges, kicks to the knees and all manner of strikes to the face targetting the nose, ears, temples and so on. When making combative moves such as punches, kicks, elbows etc the emphasis is not placed on set patterns or routines but on a continuous flurry of vicious and sustained attacks at the body's weakest points to quickly overwhelm the opponent.
Knife Block
2) Go from defending to attacking ASAP. Again consider a situation where your life is threatened by an attacker. The ideal way to escape such a situation is to avoid as detailed below, or to escape from it quickly. Krav maga teaches numerous blocks and ways of coping with all the kinds of physical attack one can encounter. However the system teaches that we should block and attack simultaneously if possible, and if that is not possible then to counter attack as soon as possible and then make our escape. Why is this the case? Well to put it bluntly unless you are Neo you can't stand and block a continuous flurry of attacks without getting hurt. Many knife attacks in particular involve not one, but numerous attacks in quick succession. As such counter attacking represents your best bet of blocking the attackers thought processes and allowing you to escape or neutralise him.
3) Three hundred percent defense. There are numerous methods of blocking any physical attack to your person. In krav maga you are trained to deal with attacks using three simultaneous strategies if possible. The first would be the hand or foot defense, which would involve blocking or deflecting a strike or maybe plucking or otherwise breaking a choke or similar attack. The second is the body defense and this simply involves turning or moving your body to remove it from where the attacker is attacking to. So for instance against a straight punch to your head you move your head and upper body to the side. The third principle is 'moving off the line of attack' and simply involves moving round your opponent so that the line of attack, that is the direction in which he is or can attack you is no longer going through you. This is important for numerous reasons. As stated above an attack will rarely make one discrete attack, there are likely to be several planned. Blocking or deflecting the initial attack and then swiftly moving to the attackers side and rear is a good way to avoid further danger and place your self in a prime position to neutralise the attacker, flee and also scan for further attacks in the blind spot that you previously had as he attacked you.
4) Situational awareness/scanning. A typical fight in a movie often involves two people facing each other and essentially slugging it out as if they were characters in Street Fighter. Numerous blows are thrown, blocked, taken and so on until a victor emerges. Being attacked in real life is rarely this simple. Attacks are made without warning, from all different angles and by single or multiple opponents. As such it's very important to be continually aware of your surroundings and to be able to recognise danger signs and react instinctively. Krav maga teaches situation awareness with various kinds of drill and training. All students are also taught when attacked to move off the line of attack so that you can see into what was your blind spot and then to scan for further attackers, methods of escape, common objects to use as makeshift weapons etc. The importance of this cannot be stressed enough!