Figure[Black to move]

First find the idea for Black. You see that his rook attacks White’s rook. More importantly, your search for loose pieces and checks turns up the potential queen fork Qxe4+, which would win a rook if the forking square were not protected by White’s queen. Black could try to decoy the guard away with RxR, but then White has a knight he can use to recapture without moving his queen. Don’t let go of the goal of budging the queen, however; with a little more looking you can find another way to decoy it: Bb5. White would prefer not to play QxB, as it leaves e4 unattended and so allows Black to win a rook with the aforementioned queen fork. Yet what else is there? He would like to find a safe square to which he could move the queen while still enabling it to guard e4. Such a square exists—he could play Qb4—but then Black plays BxN (followed by more losses for White since now his queen is the only remaining guard of the rook on c5 and the forking square e4).

Now you can see the power of Bb5: it not only is an attack on the queen but also skewers the knight behind it, which becomes loose if the queen moves. (That little two-piece diagonal cluster of White's queen and loose knight should provoke thoughts of a skewer from the outset.) Put differently, this is another case where the queen is potentially overloaded, as it is the sole guardian of the knight on d3 and the forking square (and pawn on) e4. Black doesn’t have both points under attack at the beginning; but once White’s queen is attacked, it has no square where it can continue to guard both points.

We aren’t quite finished. After Black plays 1. …Bb5, White doesn’t have to move his queen at all; there also is the option of unleashing a counterthreat against Black’s queen. 2. Nf2 has this effect: now both queens are under attack. The problem is that when White moved his knight to f2, he left his rook on c5 guarded only by his queen. So Black destroys the guard (by forcing an exchange of queens) with 2. …BxQ; 3. NxQ, RxR, 4. b3xB, Rxc4 (taking a loose pawn), and Black has won the exchange plus a pawn. Okay, but maybe White can avoid this problem by first liquidating the rooks—another variety of counterattack. After Black’s Bb5, in other words, White immediately plays 2. RxR+, RxR—and then 3. Nf2, threatening Black’s queen and doing it without any worries that his rook will end up being taken. This can lead to some hairy complications, as often is the case when a threat in one place is not met head on but is countered with a fresh threat elsewhere; so for convenience the resulting position is diagrammed in the next frame.