More about preconditions

 Let's start with a typical Aurora attack in the Colle Zukertort. This is how it might work:

Diagram 1. White to move

r4rk1/pbqn1ppp/1p1bpn2/2ppN3/3P1P2/1P1BP3/PBPN2PP/R2Q1RK1 w - - 2 4

Remember what we try to accomplish: finding the preconditions. The preconditions are related to the LoA landscape. Let me first map the obvious LoAs (lines of attack).

Diagram 2. White to move. The LoAs

What do we see?

• blacks Nf6 messes with two LoAs
• The long diagonal is clogged up

The first thing to look at is can we clear the long diagonal with tempo?

1.Nxd7

• 1. ... Qxd7 (Aurora Australis)
• 1. ... Nxd7 (Aurora Borealis)

Let's assume the Aurora Australis

2.dxc5

• 2. ... bxc5
• 2. ... Bxc5
• 2. ... Be7 (the lesser evil, giving up a pawn)

Let's assume that 2. ... Bxc5 is played. Then we get the following position after 1.Nxd7 Qxd7 2.dxc5 Bxc5

Diagram 3. White to move

r4rk1/pb1q1ppp/1p2pn2/2bp4/5P2/1P1BP3/PBPN2PP/R2Q1RK1 w - - 0 6 

3.Bxf6         getting rid of the defender of the LoAs

3. ... Bxe3+ in between move that doesn't change the result

4.Kh1 gxf6

5.Bxh7+ Kxh7

6.Qh5+ Kg7

7.Qg4+ Kh7

Diagram 4

r4r2/pb1q1p1k/1p2pp2/3p4/5PQ1/1P2b3/P1PN2PP/R4R1K w - - 4 11 

And mate in 5 follows.

This provides a baseline. It shows the LoAs. Every move of the tree of analysis is related to the LoAs. So the LoA landscape acts as a pair of scissors to prune the tree of analysis.

It is a matter of fiddling around to get all the details of the preconditions.Stockfish immediately sounds the alarm when a precondition is not met. By changing the begin position you will find out what every piece does in relation to the LoA landscape. So far I unearthed the following areas of attention:

• Black can try b5-c4 in order to chase away Bd3
• Qc7 and Nc6 can be dangerous after cxd4 exd4 Nb4 forcing white to give up Bd3
• Prevent that black gets the upperhand on e4, where he can clog up the diagonal d3-h7
• Prevent the pawnbreak e5 by maintaining the upperhand on e5
• Whenever black gets the chance to play cxd4, he prevents that you can open the long diagonal at will
• Be7 instead of Bd6 makes that dxc5 cannot be played with tempo
• Bc8 in stead of Bb7 can have an influence on the pivot square h3, in some variations
• In some lines you need to play Bf6 instead of Bxg7 in order to prevent that black can open an escape route for his king by playing f6