Petrosian and Positional Forcing Moves

I've been studying Petrosian's games in Craig Pritchett's Modern Chess book with a friend. First one of us pulls up the game in a database and screen shares. We go through the game together, each of us quickly predicting each move. We go at a brisk pace, but take it seriously, writing down each move. I use two columns: One for my move, one for the move in the game. One cool thing about guessing each move is that you don't know what you're looking for: Absolutely everything is possible. If you see a position from an elite GM game and you know there's something strong or forcing out there, you have a much better chance to find it. But when the surprising moves are mixed in with developing, recapturing, and everything else that happens in a 45 move game, they are much easier to miss. The process of reflecting on these misses can be very instructive. The next day I study the notes and then enter them into chessbase.

In the Petrosian-Botvinnik game I mentioned last time, I really enjoyed some of Petrosian's aggressive moves that a cursory examination of forcing moves (checks, captures, and threats) wouldn't necessarily catch. Last time I asked you about this interesting position:

When we were quickly going through the game, we both wrote down the move 19.a3. But some of you may have already figured out that something better is out there. Petrosian instead played 19.Bd2!. This move has a couple ideas. First of all, the pawn on a2 is tactically defended. If Black plays 19...Nxa2, 20.Ra1 Nb4 21.Bxb4 cxb4 22.Rxa7 regains the pawn. Black will play 22...Bxb2 in that position, but then 23.Rb7 would bring up the following position:

After White unstoppably captures the b6 pawn on the next move, Black's passed pawn on b4 will be a weakness rather than a strength. Black is in trouble in the resulting position.

So, the first instructive point of 19.Bd2 is that it doesn't reflexively defend against Black's threat to capture on a2. Instead, White managed to almost ignore the threat, playing the move he would have wanted to make anyway. Many famous chess authors encourage this type of thinking. Grandmaster Ivan Sokolov tells his readers that when the opponent makes a threat, you should think about whether you can:

A) Ignore the threat

B) Create your own equal or stronger threat

Grandmaster Jacob Aagaard calls something related the Shankland Rule: Look at the moves you really want to play (rather than the moves you think you have to play) and try to make them work. Grandmaster Joel Benjamin gives very similar advice.

This brings us back to the original position.

Another thing I like about the move 19.Bd2 is that it's a positional forcing move: White threatens to play Bxb4, compromising Black's pawn structure and entering an endgame where White's outpost knight on e4 is much stronger than Black's bishop on g7. White would then play the move b3, when the Black bishop has nothing to attack.

We all know to look for "checks, captures, and threats" on every move, but not every forcing move threatens to win material or deliver checkmate! 19.Bd2 is a forcing move in its own right, threatening to damage the opponent's structure.

Now that we are talking about positional forcing moves, I want to give you a position to think about. Play continued (after 19.Bd2) 19...Nd5 20.a4 Rc8 21.b3 Bf8 22.Rc1 Be7, bringing up the following position:

What do you think White should do here? Solution coming soon!