|After 1.Bxd4 Nxc5. White to move|
The winning move is 2.Bxg7 and I can see why it is winning. Not only does the move capture the bishop, it also threatens the black queen. It is a discovered attack. In the time that black needs to save his queen, white can bring his bishop into safety.
What I don't see though, is why 2.Bxc5 is not winning. Apparently the move does the same as 2.Bxg7, a discovered attack taking a piece and threatening the black queen.
As usual, this post is not about this position. I use the position as a vehicle to show you something. We look at CCT, which describes what to look for in order of forcingness. That order is handy because it prunes branches with lesser forcing moves, preventing you from calculating unnecessary lines. But now I'm looking from the perspective of what is going on. A position like this is about gaining wood. That means, that capturing pieces is paramount, and you can only postpone a capture if you have a very good reason for it. Like a check or a threat. If you postpone a capture, your opponent must too, otherwise you are not going to gain wood.
Aox gave a nice rule of thumb for positions with mutual captures: "A sequence of takes where you take first and last is usually benefitting". Whether it is beneficial or not, is based on the value of the pieces that were taken. I discovered this rule in 2007 or so, and it is very useful. But now I see that this rule needs extension, for whenever one of the parties postpones a capture by flicking in a check or a threat. I already devised this rule: "In case a capture is met by a check or threat in stead of a recapture, you win a piece when you can capture the threatening piece.". But in this case, there is more going on.
The puzzle at hand rates 1952. Which is kind of reassuring. Albeit I'm a patzer, at least I'm not alone. Let there be no misunderstanding. I can calculate why 2.Bxc5 is not winning. But that is not good enough. The average solution time is 57 seconds. Calculating a solution is both time consuming and error prone. To solve this position within 57 seconds correctly, I need to see the main ideas. I can never calculate this correctly within 57 seconds. To speed up calculation is no option, since that introduces errors, as we found out.
I feel that the only reason why I am not a 1950 rated tactician, is because I cannot see the solutions in this kind of positions.
There are two more things going on in this position. After 2.Bxc5 Rxc5 it appears that white's rook on c1 is overworked. It cannot defend both the bishop on c5 and the rook on d1. In itself that would be no reason for the move 2.Bxc5 to be not winning a piece. [UPDATE] After 2. ... Rxc5 3.Rxd8 Rxc1+ white still would win, now the queen. If it weren't for the check, which gives black the opportunity to recapture the rook on d8. I hope you can still follow me.
I hope that you can see what I'm after. I want to tell the narrative of this position in terms of captures and postponement of captures. I want to devise some rules that govern the story of the initiative. And what is even more important, I want to be able to see these rules at work. My posts about the initiative generated remarkably little comment. But the story of a combination is told by the vicissitudes of the initiative. I want to see it at work.