Here is a slightly different sort of position. It begins not with a check but with an observation. White has a rook on the seventh rank, a great position. In addition to threatening to wipe out Black’s holdings on that rank, the rook also threatens to support attacks against the king if another White piece—the queen—can be added to the seventh rank and serve as part of a battery there. So in addition to looking at what he can do on the f-file where he already has a battery of one sort (but with attacking possibilities that are inconclusive), White should think about trying to convert these assets into a horizontal battery on the seventh rank. A typical way to do this is by moving the rook over to make room for the queen to come down the board, but that would be impossible to do effectively here. Another method—and the winner in this case—is to move the queen over preparatory to dropping it down. Thus White plays Qh3 or Qh1, looking forward to Qh7—and notice that this will be mate unless something changes. In a sense Qh3 is nothing more than a type of mate threat we have seen many times before, with White adding an attack by his queen to a square next to the enemy king that he already attacks with one of his other pieces.

The reason Qh3 looks so strange is that it leaves the rook en prise to Black’s king; Black’s obvious move is to simply play KxR, ending the threat. But if you picture the position that results from these moves, perhaps you can see why White allows it: now Black’s king and queen are on adjacent ranks; the king can't advance any farther up the board because of White’s pawn on g5; and White’s queen now has a clean shot down the h-file. These elements suggest a possible skewer on the back rank of the kind we have seen recently. White thus plays Qh7+, forcing Black to move his king to e8 or f8. With Black’s king and queen now aligned again, Qh8+ skewers them and wins the queen next move.

The lesson is to make sure you are not so distracted by your battery on the f-file in a position like this that you do not see a critical vulnerability in Black’s position: the alignment of his king and queen on the back rank. This should cause you to think about a skewer, which would be decisive even if achieved at great cost. The possibility becomes more plausible when you see that the h-file is open. You can afford to let the rook go if it will enable you to get your queen down the h-file safely and effectively, which you can do here with a threat that makes Black’s reply easy to forecast.