To make a few comments on Ken McGrew's post:
I think this assumption is the problem. O Sensei, for example, insisted on attacks coming from at least three steps away. His thinking, reportedly, was why let an attacker get closer than that.
Correct, why would you "let" a person get any closer than this? In fact if I am in that much control of the situation I will not "let" him get even that close. The irony of the situation from a empty hand situation is that I am having to use my body to defend myself, then I am not "letting" him do anything, I do not have a choice in this situation and must deal with it and at whatever distance he is at. Rule of 21 implies that he has closed the distance, if he is 3 steps, then he is 1 step, and then no steps. We would like to think we have that much control of the situation, however in reality we don't if we are fighting. That is the whole issue I have with parity. We assume it and assume we have knowledge and theoretical control over something that in realit we probably do not.
So IMO, we need to set up our "problem sets" in which we have lost control of the situation and we don't have control at 3 steps. Simply put we are either already winning or we are losing. It is one or the other, unless it is a sport like boxing, we don't have parity. That is why they have a ref in boxing...if two boxers could maintain parity....you'd have no need for a ref!
So, your first paragraph assumes alot in the situation, IMO, that is you have that much control and knowledge. This paradigm strongly favors "timing" as a factor of success and IMO and experiences is why most martial methodlogies fail in the real world. timing is a poor strategy to rely on.
Sucker punches: it is only a sucker punch if he suprises you and punches you, otherwise it is not a sucker punch! sucker punches by definition and situation are the product of the element of suprise. That is, he has the jump on you, has used this as a tactic to achieve some degree of suprise and overwhelm you in an attempt to dominate you. How you deal with it is you either quickly establish your structure/integrity, or you don't. If he connects and knocks you out...well game over, if he doesn't...well then what do you do to turn the fight back in your favor? Timing doesn't work, ducking might by you a second, but what then.....what is your structure like? how do you follow up and close his OODA loop?
Knife: they suck, if he has one and he has closed distance and is in charge, you are going to get stabbed and stabbed probably over and over. Unfortunately, you cannot really gain control of the knife until you have disrupted his OODA process and his structure/integrity before attempting to control the knife. sure you can block and you might even get a hand on his arm to slow down the attacks, but the fact will still remain until you can go through the steps of fixing your integrity then disrupting his, you are really not going to turn the tables. So, the quicker you can do this, the better off you will be. the fact that he has a knife doesn't really change the process, it does add a degree of difficulty and of course it has upped the stakes dramatically, and yes it sucks, but you still have to go through the same process.
Getting off the line: I don't really like this paradigm as it assumes a degree of control that you may not have. In theory, yes you need to get off the line of attack, and there are probably some semantics in this statement, but I think for most we think of getting off the line as a particular movement of body position and control...the paradigm assumes too much I think for most. How do you get off the line if he is on your back? how do you get off the line if he is in the mount, how do you get off the line if he is clinching you up against the wall and stabbing you? again, in theory, yes, you want to change the angle of your defense to place his posture at a position in which he cannot effectively attack you, however, to me, we need to look at much more in the situation than an external manifestation of physical movement of "getting off the line". This IMO is why we need to consider what is going on inside ourselves, how to I quickly and intuitively move to regain my structure, then affect his and gain the advantage to control him again?
". If someone comes in slower you can back away to maintain proper distance. "
My years of experience in teaching CQB have proven this to be a fallacy. You cannot back up and maintain proper distance and be successful. Sure, you may delay the attack for a brief moment. It goes back to OODA. If you are back pedaling, then you are not in control of the fight and he is, so in order to gain control, you will eventually have to do something to disrupt his process which will involve entering his structure some how. Aikido randori also demonstrates this concept very well. Rule of 21 is all about this as well and is another way of explaining the concept. I have found it better to quickly Observe/Orient and then Decide/ACT...this translates in most cases in entering very quickly with good structure/integrity and disrupt his process. You do this by moving forward and establishing control.
Back pedaling is equal to the concept of "bargining" that is, I am trying to "by time" and delay the inevitable. Our natural instinct is to do this, especially when we are presented with a danger we have not processed. I equate this to putting your hand on a hot stove accidently, our instincts are to pull away and in that case it works, however in a fight, it typically does not, so IMO and experiences it will usually end up bad for us and a better instinct is to program ourselves to do something more "proactive" or different.