With Black’s king out from the back rank and White’s queen now behind it, the threat of a skewer again is live. Inspect any checks White can give. There are four, all with the queen: Qb6, Qd6, Qe8, and Qg8. As we have seen, the check of greatest interest frequently is the one that gives the enemy the smallest range of replies—here Qg8, which seals off the king’s flight squares on the seventh rank and so requires Kf6 as Black’s only legal reply. Presto: the king and queen once more have been forced onto the same file. Now White’s queen moves to f8, applying another check, forcing the king out of the way, and then winning Black’s queen with QxQ. The queen does all the work by itself.