Introduction; Simple Cases We turn now to a different pattern: the rook

that blocks and then unmasks an attack along a diagonal by a bishop or queen. In a way the pattern is the reverse of a bishop discovery; this time the unmasker moves vertically or horizontally while the attacker runs on a di- agonal. Since the mechanics involved are fa- miliar, we won't spend quite as much time on the rook as we did on the bishop or as we will on the knight. Still, there are some differences between the patterns that are worth a few moments of special attention and visual ab- sorbtion.

First, an unmasking rook usually has a harder time giving check than an unmasking bishop does. The bishop can act as a dive bomber, coming in on a diagonal to attack the king from above or below; the rook has to deliver check by moving straight down onto the king’s rank, or (less often) over onto the king’s file. Either of these moves can unmask an attack, as we shall see, but they are less common than the bishop’s strike against, say, h7. The significance of this is that when the rook discovers an attack, the distraction it creates more often is not a check but instead is some sort of mating threat, typically against the back rank. And discovered checks—i.e., moves where the piece behind the rook gives the check, rather than the rook itself—also make up a relatively large share of rook dis- coveries. Finally, discoveries by the rook also look different than discoveries by the bishop. The rook kernel isn’t as easy for the untrained eye to see as the bishop kernel; the eye is ac- customed to looking up and down the files but not so accustomed to scanning the diagonals in the same way. The positions in this chapter are meant to build that visual habit.

Dg363: Let’s begin with positions that are comparable to the first studies in the chapter on bishop discoveries. There, a bishop mas- ked a queen or rook that was ready to attack an enemy piece along a file; here, a rook

masks a bishop or queen that is prepared to attack an enemy piece along a diagonal.

Dg363: White to move

There, the bishop unmasked the attacking piece with a diagonal move that checked the enemy king; here, the rook unmasks the at- tacker with a “vertical” move—a move down a file—that checks the enemy king. In either case, the unmasked piece has time to make its capture after the check is fended off. Where does White have the makings of a dis- covered attack in this first example to the left? The answer presents a new pattern: it’s on the diagonal f1-h3, where the rook masks an at- tack by the bishop against Black’s queen. The questions about the idea's execution are famil- iar: what violent move can the rook make that will require a time-consuming response from Black, giving the bishop time to take Black’s queen? The answer, of course, is a check: Rxg7+ requires Black to play KxR (or move his king); and now White plays BxQ.

Dg364: White to move

Dg364: Where does White have the makings of a discovered attack? This position is simi-

lar to the last one and is offered mostly for the sake of pattern reinforcement. They differ in trivial respects: the White pieces comprising the kernel of the discovery are another square apart, and this time it’s the queen rather than the bishop that is unmasked. But the execu- tion is about the same. Black’s queen starts out as a bad target because it has protection from the knight on g7. White can eliminate the guard while unmasking the queen—and can do it with check: RxN+. After KxR, White plays QxQ and wins a queen and a knight for a rook.

Dg365: White to move

Dg365: The general idea here is the same as before: see the queen-behind-rook pattern for White, this time running in the other direc- tion; notice the Black queen, poised to be taken by White’s queen if the rook can move out of the way with check. Here the rook’s check probably is of its most common type: the move to the back rank, in this case with Re8+. The check easily is defused with RxR, but then White wins the queen with QxQ.

Dg366: Black to move

Dg366: Where does Black have the makings of a discovered attack? There is nothing on

the files or ranks, but along the g1-a7 diago- nal Black has a bishop masked by a rook. Does the bishop have a suitable target if the rook moves? Yes, in White’s unprotected knight. As discussed in more detail in our work on forks, an unprotected or “loose” piece always calls for a look at whether it can be taken with a tactical maneuver. Here the question is whether Black can vacate his rook from c5 in a manner that is time-consuming enough to allow him to take the knight a move later—and that doesn’t lose the rook. (Since the payoff of the discovery is just go- ing to be a knight, Black can’t afford to sacri- fice his rook the way he did in the previous positions.) So Black looks for safe rook checks and finds Rc1+, where the rook is covered by Black’s bishop at e3. The move forces the king to move to a2 and then allows Black to play BxN safely.