Figure[White to move]

White’s knight is on a dark square; so are Black’s queen and rook. Thus there is a forking square at f3 which is easy to overlook but should be made no less visible to you by the presence on it of White’s own queen. You need a move for the queen that forces a response from Black, making Nf3 possible. You might first see QxN, but look harder for a check or capture that doesn’t require you to sacrifice the queen. Correct is 1. Qa8+. 1. … Kh7 then is forced (Ne8 just loses the knight); and 2. Nf3 can then follow. White wins the exchange.

Most of our forks so far have involved the enemy king as one of the targets, but not this one. When the enemy king is not a party to a fork you are considering, it is important to pause and ask whether either of the forked pieces would be able to break out of it and do damage or seize the initiative with a check. In this case that’s not a problem, though; neither Black’s queen nor his rook has a good option.