dear Liza, a hole

When a position is very crowded, I have often problems to find the right continuation. The next position took me 14 minutes to find the wrong move.

Diagram 1. White to move

 r5r1/3b1nk1/p2p1ppb/1ppPp3/4PqP1/2P1NPN1/PPB1QK1R/7R w - - 1 1
[solution]

I'm going to ponder about what exactly is the cause of my failure, and which knowledge is needed to prevent such debacle in the future. Feel free to comment already, that is helpful.

UPDATE
It took quite some time to grasp what is going on exactly in this position, but with the  aid of the comments I was able to unravel it in the end.

The problem with  this position is, that with  T+E (Trial and Error) you soon dismiss 1.Nef5+ Bxf5 2.exf5 as too slow. Aox even called this move "silent", albeit between quotes. Only when everything else fails, you might come back and have a deeper look. And that is exactly what we try to avoid. How can we think about this position with as less calculation as possible?

Somewhere I defined the PLF (PoPLoAFun) system as a method to get on the track of the most immobile pieces. There are two completely immobile pieces here, the black knight and the g-pawn. When they move, a piece is immediately lost. They are immobile because they have a Function to fulfill. All other pieces can move a bit, as long as they stay in contact with their Functions. Have a look at diagram 2.

Diagram 2. The knightfork or duplo attack. White to move

Legenda:
Square = target
Circle = attacking square

The duplo attack is pretty easy to spot. It makes g6 an immobile defender. With a duplo attack, you have no free move. You have to attack two targets with one move. Since the opponent can only move one piece out of the way, the other piece is lost. Immobility due to lack of time.

But why does 1.Nef5+ Bxf5 2.exf5 work? Why is it not too slow?

Diagram 3. The triplo attack. White to move

Legenda:
Square = target
Circle = attacking square 


The point is, that fxg6 is a triplo attack. It attacks the knight (1), which has a function as defender of the B.A.D. (Barely Adequate Defended) bishop (2), and it captures g6 which has the function as the defender of the attacking square h5 (3). Thus making the knightfork possible.

 With a triplo attack, you have one free move. That is exf5. Which looks silent, but isn't. Black has 3 defensive task to fulfill:

• Get the knight out of harms way
• Get the bishop out of harms way OR defend it extra
• Get one of the targets of the knightfork out of the way OR defend the attacking square h5 extra

3 defensive  tasks takes black 3 tempi to accomplish. That gives white 2 tempi to carry out his attack. Black cannot accomplish his 3 tasks in 2 tempi. White's tempi: exf5 and fxg6.

The plf system provides everything you need to know to focus your attention on the relevant squares and pieces. With hardly any calculation at all.