- Target placement
- Exploiting immobility
- Opening of the line of attack
- Connection to other tactical themes
Let's have a closer look to the pin from our starting point.
|Diagram 1. White to move|
Here you see a duplo attack at full force. 1.Bh2 attacks two targets with one move. One target is attacked directly, the other target indirectly. It wins because black needs two tempi to save both targets in one move. This is a clean pin. Black has no defensive resources whatsoever at his disposal.
What can we say about value in the above in the position above?
- The value of the attacker doesn't matter
- White wins the piece with the lowest value since the other piece can escape
- If the value of the head piece is lower than the tail piece we call it a pin. Otherwise we call it a skewer.
Now let's add some defensive resources.
Maybe I'm going to treat the following not in the most efficient order, but I have no way to know beforehand what the right order will be, or what will proof to be redundant. So you will have to bear with me. In the later to write summary I will make it up with you.
|Diagram 2. White to move. Imagine as if the kings aren't there.|
If white plays 1.Bh2, we can no longer make use of the pure value of the black pieces. If a piece is defended, the value to gain by capturing it, is calculated as target -/- attacker (-/- is the symbol for the minus sign). In the position above, white doesn't gain anything from the capture of the knight, since the calculated value of the gain is 3 -/- 3 = 0. If the black knight is replaced by a rook, the gain would be 5 -/- 3 = 2 points.
In fact it doesn't matter if the head piece is defended by the tail piece or by any other piece. So there is no need to add a separate scenario for the defense by the tail piece. The tail piece is just another defender.
Second scenario: a protected tail piece
A protected tail piece alters the calculated value of the potential gain to the value of the tail piece minus the value of the attacker. 9 -/- 3 = 6
When there are defenders involved, you no longer work with the pure values of the targets, but with the calculated values, which means the value of the target minus the value of the attacker.
The conclusions above aren't limited to pins only, but can be extended to all duplo attacks.
All the above may sound a wee bit trivial. But it clears the head for what is to come. So stay tuned. . .