I am often asked questions about criteria used to evaluate chess positions. This is a subject I find very interesting: my first book, Elements of Positional Evaluation, was written 30 years ago on a typewriter and addressed this subject extensively.

One interesting criteria is “space”. In order to discuss space, we should first attempt to define it. How about:

Space is the amount of area (roughly measured in squares) between your pawn chain and your first rank (including the first rank, but excluding the squares of the pawns, which are inaccessible to your other pieces).

Let's try a test of this definition: As the pawns disappear, the amount of space becomes more amorphous and, as seems reasonable, disappears entirely in a pawnless endgame. That intuitively makes sense; therefore so far, so good.

Having space is, hopefully and usually, good for all those advantages we hold near and dear:

* Allows more room for your pieces to maneuver,

* Gives less room for your opponent's pieces to maneuver, and

* Gets your pawns closer to promotion, which also makes sacrificial promotion combinations possible.

But now comes the important part. Consider the following pawn structure:

I think it is pretty safe to state that, by any measure, White has a ton more space. Furthermore, if we place the pieces as follows, his advantage due to this space is devastating:

A great triumph for White's space advantage!

But suppose we leave the “space” unchanged (and even the King positions) and just change the positions of the other pieces:

Now Black's pieces have managed to “get around” and penetrate the “White space”, resulting in an enormous reversal of fortune. You may think this example is far-fetched, but such penetration occurs fairly frequently. For example, this is often what happens in an Open Sicilian when White castles kingside and correctly pushes his pawns for a kingside attack. But if that attack is misplayed, fizzles, and Black breaks through in the center, then White's advanced pawns often leave him with an exposed King in the middlegame, and this can be the deciding factor in Black's favor.

So, although the above diagrams are extreme examples, they help prove an important point! Space in and of itself is not an inherent advantage; it is a means toward an advantage. The real advantage of having space is that if utilized correctly, it allows your pieces to do more than your opponent's pieces (“better army activity”). No more, and no less. If a spacial advantage does not incur an activity advantage, then it can be – and likely is – meaningless.

As another common example, consider a King-and-pawn endgame with both Kings centralized and the pawns locked, with one side having much more space (you can even use a similar pawn structure to the previous examples). Then the side having more space is often at a disadvantage since the enemy King has gotten “behind the lines” and can be used to “elbow out” the King whose side enjoys the space advantage. As a simple example, consider the following position with Black to play:

Here Black, with the space advantage, loses because White has the opposition, but also because Black's pawns are so advanced and vulnerable.

So, on the average, having more space is an advantage, but the advantage usually has to be in the form of more activity. Of course we could state something similar about many so-called advantages (for example, “time” – see the next paragraph), but it should be clear that the real end goal you are trying to achieve is more active play, not space.

We could make the same argument about time as we did about space. For example, in a given position I can give you free extra tempos, but if you use them unwisely and place your pieces on squares less effective than they were (or just have no effective way of making them better; zugzwang being the extreme example), then having “extra” time would not be helpful. So again we see that time, like space, takes a back seat to the real goal – having more – and better – things to do with your pieces.

In Elements I designated the number of squares to which a piece can move its mobility. Mobility is extremely important since piece value is highly correlated with mobility – a Queen is more valuable than a Rook because it can also move like a Bishop. But the value of mobility in a real position can, like space, also vary, in that a piece can have lots of useless moves (not usually, but it does happen). Therefore the real goal is good piece (or in total, army) – activity. No matter how you define activity, if your pieces have lots of good things to do – mobile, flexible, attacking key points, etc. – then that is the real advantage.

That is why, in my book, I call space a pseudo-element. I used that term to mean that space does exists as an understandable and useful concept, but is not really an elemental basis to evaluate a position. So what is a good measure of positional, static evaluation? From the above, you can deduce that I must use total piece activity to cover the useful byproducts of space and time. I claim the four most important static evaluation criteria, in order from most to least important, are:

* Material

* King Safety (you can make this #1 if the King is extremely unsafe!)

* Total Piece Activity

* Pawn Structure

The fifth, “non-board” consideration, is the clock/time factor, which can even become the most important consideration in the case of severe time pressure. Time remaining on the clock is always a big factor in faster time control games.

Note: to get the proper dynamic evaluation you must mentally move the pieces, find each player's best moves, and see what can happen!

It is not that pawn structure is unimportant – it is, or it would not be on this list! For example, in common positions where the material is even, both Kings are safe and both armies relatively equally mobile, pawn structure can easily be the deciding factor. But otherwise many weaker players greatly overrate pawn structure and think they are winning when their pawn structure is somewhat better, even in the face of clearly more active enemy forces! Similarly, sometimes players strive for more space and get it, only to find that the active and flexible enemy pieces make their space advantage rather moot! This happens in many openings, but Open Sicilians and the Modern Defense are two that readily come to mind.

In summary, next time you are considering pushing pawns to make space, evaluate the likely result to make sure you are not just weakening yourself but actually providing an advantage for your army. If so – and there is nothing better to do – go for it! Evaluation is an extremely important chess skill, and we will address it much more in future Thinking Caps!