OpenChess

I was reading something about alternative search algorithms in chess, where the author commented on the programs performance saying something like....
“The programs poor abilities in defensive positions.”
“The programs poor abilities to find good defensive moves.”

It got me thinking....
What really makes a position “a defensive position”?
What does it really mean to be “on the defensive”?
What does “being under pressure” really imply?
If one side is “on the defensive” is the other side then by definition “on the offensive”?
Is it possible to objectively measure how much one side is “on the defensive”?

Is a defensive position just a position where one has only one (or a few) good moves, and a offensive position you have many moves with approximately the same eval?
Hmmm... then all positions with a deep tactical win would be a defensive position (for the side with the tactic to win), as one move is significant better than all others.
Therefor that can not be a good definition.

Is the offensive side on the offense because he can deviate from the principle line at only a small cost in eval, thereby not feeling the pressure of absolutely needing to find the very best move.
And is the defensive side on the defense because any deviation from the principle line would come at a high cost in eval.
And if both conditions is true, then we have a defensive position?

If so, maybe it would be possible to measure and classify positions by their defensiveness?
The more options you have to deviate from the principle line without hurting your eval “to much” the more you are on the offensive.
And the fewer options you have through the search tree to deviate from the principle line, and the more those deviations cost you, then the more your are at the defensive.

Any thoughts, ideas, comments and critic is highly welcome.

I remember once in a tournament game playing the black pieces from this position

rnbqkbnr/ppp2ppp/3p4/8/2B1P3/8/PB3PPP/RN1QK1NR w KQkq - 0 6
being up 2 pawns but more importantly being “on the defensive” for the rest of the game.

Any thought on what constitute a “defensive position” is highly appreciated.
Examples of positions where the eval is about even, but where one side is clearly having to defend well for the next couple of moves is even more so appreciated.

Thanks.

That looks like a "Goring gambit" type of position where black eats from d4 to c3 to b2 while white develops. However, it is probably NOT the kind of opening to play against computers today. Most gambits give a strong initiative, but they also offer the side that is ahead several opportunities to make a mistake. If he plays perfectly, white can end up looking foolish.

I think the article you read really doesn't apply very well today.

I totally agree with you.

Today’s programs are very good at defending complex/difficult positions.
I not saying or implying that gambits are good.
It was just my attempt to provide an example of a defensive situation.

What I was really after:
An example or two of a defensive position?
What makes the position defensive?
Could it be explained in such a way that the defensiveness of the positino could be objectively measured?