An important principle in chess is the concept of the “forcing move”. A forcing move is one which requires the opponent to reply in a certain way, or which greatly limits the ways in which he can respond. Essentially, a forcing move is either a check, a capture, or a threat. In the case of a check, it is the rules which force the opponent to respond – he must get out of check. Capturing moves and threats are also usually forcing, because while the opponent may legally be allowed to make any move, most of the moves will be bad.
When we calculate variations, we should always pay attention – and calculate first – the forcing moves. This is because these are the moves most likely to achieve something, and they are also the quickest to calculate, since the opponent can only make a limited number of responses.
If you calculate all the forcing moves first (even if they seem silly) you will avoid a huge number of miscalculations and oversights. This is not merely advice for beginners – even strong players can easily get wrapped up in one specific long variation, while missing what is right in front of their eyes, due to not looking at every forcing move. This happened in the fourth round game of my most recent tournament, the Cleveland Open:
The game was a fierce battle against IM Goran Vojinovic and reached the above position shortly after the time control. My opponent had sacrificed the exchange to gain the strong passed d-pawn. However, I had managed to control the pawn and covered my king as well. Now it is White’s own king which is more exposed, while his a-pawn is also a serious weakness – and if it falls, my b4 pawn will quickly promote.
Since my queen is attacked, there are two moves to consider here – 43…Qa1 (threatening 44…Qg1+) and 43…Qe5+, possibly followed by …Qa1. I felt that one – or possibly both – of these moves should win.
It is pure calculation that allows a chess player to decide between these two moves. It should not be a very hard task, since there are only two candidate moves, and the opponent has a very limited response after each of them, since one checks the king and the other threatens mate. Additionally, there was plenty of time on the clock. Nevertheless I was unable to choose the right move and not only overlooked the very response to my move, but also missed the win in the rejected variation.
Before continuing, you have the opportunity to try to calculate the variations and decide what you would choose.
My initial intention had been 43…Qe5+. After this White has only two responses – 44.Ng3 and 44.f4.
After 44.Ng3 Black can play 44…Qxc5, since 45.d8=Q is met by 45…Rxd8 46.Qxd8 Qxf2+ 47.Kh1 Qe1+! followed by 48…Qxg3+ and mate. (All the variations given in this article can be found in a diagram at the end, if you have trouble visualizing them.) Meanwhile, after 44…Qxc5 bishop discoveries such as 45.Bxh7 don’t work because Black can play 45…Rxf2+. Therefore Black wins the important c5 pawn and I considered the position to be pretty much winning, although it was possible that there could be an even more direct win with 43…Qa1.
After 44.f4 the black queen is under attack, so I only considered 44…Qa1. Thus the question was whether to play 43…Qa1 immediately, or first play 43…Qe5+ and induce the move f2-f4. Now Black again threatens 45…Qg1+. Moves like 46.Ng3 or 46.Qf2 fail because – since f2-f4 has been induced – Black can play 46…Qxa2, forcing the trade of queens and winning easily. Does White have another way to defend against 45…Qg1+? Yes, there is 45.Ng5. Now Black needs to capture on a2 and force the queen trade, which should normally be decisive. But doubts quickly arose whether after 45…Qxa2 46.Qxa2 Bxa2 Black can deal with White’s threats.
I looked quickly at 47.Bxh7, which at first glance seemed the most dangerous, and it looked scary for Black. I figured I would have to sacrifice an exchange back, but I did not know what was going on. Now it is clear that even better is 47.Nxh7, which is winning for White. I had a feeling that maybe in this long variation Black was winning somehow, but it was all unclear, so I moved on to 43…Qa1.
Black threatens 44…Qg1+, so this is a forcing move – White has only a limited number of responses. I saw the moves 44.Ng3 and 44.Ng5.
After 44.Ng3 it seemed that Black can safely take on a2 with the queen. This does not force the queen trade (since f2-f4 was not induced) but nevertheless it appeared that Black should be winning (incidentally, this is not really true – after 45.Qd4 the situation is dangerous, since 45…Qd5 is met by 46.Rxh7+!).
Therefore I calculated 44.Ng5. This would be met by 44…Qe5+, since the bishop on f5 is now unguarded. I calculated 45.f4 Qxf5 46.d8=Q Rxd8 47.Qxd8 Qxf4+, and Black is easily winning.
Therefore, although I had my doubts about the position after 44.Ng3 Qxa2 and a queen move, I played 43…Qa1. I had a sense that I was blundering something, and checked carefully to see if there were any other defenses besides 44.Ng3 and 44.Ng5. Nevertheless, I did not see the very next move, which came immediately – 44.Rg5!
Somehow this move entirely escaped my vision. Perhaps part of the reason is that it is a one-square sideways shift by a rook. The rook on h5 had been a dangerous piece earlier, and I had had to spend several moves to defend h7, and various dangers remained (for instance, there had earlier been some tactics where …Qxa2 is met by Rxh7+, deflecting the bishop). However, now it is plain to see that the Rh5 is mostly out of play, and White desperately needs to neutralize the dangerous Rg7. Maybe somebody coming fresh to the position would easily see 44.Rg5, but since that rook had been very threatening some moves earlier, I did not see it as a piece which White would want to trade.
After 44.Rg5, the position soon became equal and was drawn. Basically this was not a bad result, since I was leading the tournament and drawing with black put me in a good position in the last round. In the end I tied for first, although winning this game would have pretty much guaranteed me clear first a round before the end.
Later it became clear what elementary oversight had prevented me from winning. Have you seen it yet?
In the variation 43…Qe5+ 44.f4:
I had only looked at 44…Qa1, and quickly became immersed in the line which I gave above – 45.Ng5 Qxa2 46.Qxa2 Bxa2 47.Bxh7. However, this was my mistake. I did not look at other forcing moves here. If I had, I would have easily found 44…Rxf5!
Since White cannot take the queen due to 45…Rxh5 mate, he simply loses a piece and the game ends. This means that my opponent would have to meet 43…Qe5+ by 44.Ng3 Qxc5, and Black should have a steady win.
The moral is to always look for forcing moves when you are calculating. In particular, when the position is as explosive as the one in the above diagram, you should consider every forcing move, even ones that seem bad at first. Assumptions are your enemy when calculating. As a result I ended up calculating deep and long variations, when the win is right there, and evident within three moves of the position in the game.
In part two we will see this entire fascinating fighting game which I played against IM Vojinovic. Here are the above annotations on the board which you can move through using the arrows.