Introduction

What does tai sabaki mean? Quite literally it stands for "body movement" and encompases stance work, footwork and more generally both how you move and how you move your opponent. This is the cornerstone of all martial arts and extra care should be taken initially to be sure that this is done well. One master was known to watch classes merely from the hips down and could easily then tell students what techniques they were or were not capable of doing. He said that he need look no higher if the tai sabaki was wrong.

Certainly people can see why one needs to move in a martial art, but there is quite a bit more to it than chasing the bad guy. Jujutsu is a positional fighting system. This means that the tools you have available to you depend on where you are in relation to your opponent. Can you punch someone standing behind you? How about to your side? Actually you can briefly disarm your opponent simply by body movement (no this isn't a long-term solution). For a smaller, weaker person this can completely determine success or loss. Another thought has to do with the influence of sports. really if you are more or less equal to your opponent, you can exchange blows. This makes great sport, but the assumption is that striking is rendered safer since there is no disparity of force. Even more crucial is when there are weapons involved and exchanging blows is immediately fatal.

We advocate initally having very deep stances, i.e. having your center as close to the ground as you can. This does two things, the first is merely practical in that it builds up your legs to work through their full range of motion. Most people walk using only a fairly small range of motion with their legs and hips. Once this is exceeded, strength falls off drastically. Since you will be moving people in a variety of ways, we don't want you to suddenly lose power in the middle of a technique. There is a safety issue here, since the most likely way for novice to get hurt learning a throw is to lose stability/strength in the middle of a technique and fall.

Secondly, we are a grappling style and the distance between opponents is usually less than a handspan (on the order of 6 - 8 inches or about 15 - 20 cm). Changing the horizontal distance is not usually much of an issue at this point, but making sure your center of gravity is lower than you opponent's is critical. Stances are actually designed for very close in grappling work where you must change your relative positions quickly while having maintaining stability with a potentially much large opponent hanging on to you.

A linear force is relatively easy to counter, but once that involves a curved path is quite likely to disrupt balance. Therefore being able to generate force while being stable in motion is very desireable. Dropping or raising your center of gravity as needed is a quick and effective way of countering any off-balances from your opponent. Generally though, as speed increases, stability drops off.

In practice, you will start from a normal walking position in most techniques, but once engaged you will doubtless endup in a variety of positions. We will cover the following basic techniques.

We will also start several drills for stability.

Finally, we have several footwork drills

Note that we are just concerned with moving here. I've found that a few weeks spent focusing on this will have a large payback in terms of how quickly you progress, so it is time well spent.

Tactics

There are various things one can do with the footwork rather than just  outrun the bad guy. This is the realm of tactics (defined as the military science of deploying weapons effectively against the enemy, versus strategy, which is the military science of command). Here is a discussion of the tactics you may use with your footwork.
Footwork is not the same as body movement, but falls under the heading of basic mechanics. If you are not aware of how you can move your feet, you cannot move your body. The classical approach to body movement is that there are really only two motions, entering (irimi) and turning (kaiten). Any combination of the two is called tenkan. Yes, this system is very simple, because it covers lines and parts of circles and combinations of these, so any trajectory can be described (or at least approximated). In practice, however, there are six basic ways to locomote and each of them can be used to generate each type of taisabaki. For example, entering (irimi) can be generated from  walking or shuffling pivoting, twisting or just jumping forward.  Obviously combinations of these can get pretty complex footwork. That is what these drills are part of the syllabus. Even though the analysis of body movement is admirably simple, this does not convey how you want to use it. So what follows is the sorts of things we do with taisabaki in practical applications. Any of the basic taisabaki can be used for the following tactics. The footwork that goes into the body movement should be viewed separately from the movement itself. Said differently,  the goal (i.e. which taisabaki) is dictated by your tactics and the mechanics to accomplish it are given by the footwork.  

The taisabaki used are