Black's Move 18 in B99 Sicilian

Hi,

I just had this game against the legendary Lance in his simul. I'm sharing this only to ask about a specific position/moment in it -- black's move 18.


I generally "understand" my other errors and engine recommendations, but would like more clarification in human terms about black's move 18. The engine says only through Qc5 shall ye be saved (gaining tempo on rook, but anything else?) and all other moves shall send ye to a early demise (changing almost +0 advantage to +3 for the rest of the game). I can't really understand why this is the evaluation in this position (why Qc5 is mandatory), so any help would be appreciated. Thank you in advance!

Hi,

Did not go into detail, but my comments on the position after move 18 for black:
- From human perspective black's position looks very tough, because incoming g6 move will tie down the rook to defense
- Based on the above I think black should look for a specific way to activate, the computer finds Qc5 (which is not an easy move imo to find) and the logic behind it is:
- the rook will be tied down to f7 later, and the rook does not have any quick ways of activating
- Qc5 ties the queen to the defense of rook and, most importantly, sets up a tactical way of activation via later Ne5 with
the idea if Ne5 fxe5 Qxd4, because the queen no longer protects the rook
- additionally the queen on c5 supports b5-b4 move later if necessary (currently the rook defends b4)

After move 18, white has the strong threat of f5 to open the black king.
Qc5 is played to protect the f5 square, making it harder for white to play f4-f5.

The answer is centralisation. On c5 the queen acts towards central square d4. The tactical twist ...Ne5 is another centralisation.
...Ne5 is often a key move in this kind of position.