Figure 2.2.11.11[Black to move]

Here's yet another example of how the prospect of queen forks can figure into defensive thinking. The two sides are fighting for control of the center and especially of the e4 square. Black sees that the White pawn there is protected twice but that he attacks it three times. In his mind’s eye he plays 1. …Nxe4, 2. BxN, RxB; 3. RxR, QxR. But before executing this sequence he must ask the sorts of questions we have been discussing. First, would this liquidation of the position leave any open lines at the end that would allow the enemy queen to attack the Black king? Here Qg5 would be available to White, and from there the queen would join the f5 knight in attacking g7—threatening mate. Indeed, that move already is available. What prevents it from working is the absence of a second target: the queen would be aimed at the rook on d8, but its path would be blocked and the rook would be guarded. But after the exchanges Black imagines on e5, these obstacles would be gone. Indeed, the resulting position would be one you saw about five frames ago: it leaves a fork for White. So the sequence Black imagines must not be played; after it is complete it results in 4. Qg5, Kf8; 5. QxR+, Qe8; 6. QxN.

This example shows how a few precautionary questions, asked as a matter of course before entering into a series of exchanges, can save a lot of trouble at the end. You carefully imagine how the board would look after the series, including any new open lines and loose pieces; and you then ask the same questions about that resulting position that you ask about positions in front of you: would either side have any loose pieces that could be attacked while giving check or threatening mate? If this seems like a demanding position, note again that the mate threat Qg5 is available to White from the beginning. Both sides should be conscious of this. It means that if White’s queen were able to attack anything loose from g5 he would have a working fork, so any sequences Black attempts have to be inspected to make sure they don’t produce that outcome. The moral: if your opponent is a move away from being able to create a mate threat, no matter how ineffectual, keep a careful eye on it as the potential basis of a fork.