So I agree, if subverting protection is considered chasing, as the Appendix chase tells us, this looks like a mutual chase. Yet it is explicitly mentioned as a chase. The original (translated) text said:
(Emphasis mine.) Apparently they later had second thoughts about this guide line, as they added the Appendix chase, where the fact that the Rook does not move is suddenly NOT reason to disqualify it as a chase anymore. There it says:19. When a Rook cannot move because of an opponent's Knight, the Rook cannot be perpetually chased, regardless of whether the opponent's Knight is protected. (See examples in Diagram 39, 40, and 41)
In Diagrams 39, 40, and 41, the Red Knight is not protected but because the Black Rook doesn't move, it is not considered as a perpetual chase. On the contrary, each of the Red moves attacks the Black Rook and this is a violation of the rule. Red has to change.
While in this case, the Rook is also statically attacking the Horse, and the Horse is pinning it! The only difference between diagrams 39-41 and the Appendix is that in the Appendix the protecting Cannon acts from the side, i.e. along a ray not intersecting the Rook.Explanation:
Red keeps moving its Pawn to keep the Black Knight "unprotected". This constitutes the Red Rook perpetually chasing the unprotected Black Knight. Red is violating the rule.
If we take this seriously, the conclusion must be that you re not allowed to chase by subverting protection if the opponent is idle, but that counter-chasing by protection subversion while you are being chased apparently is not a reason to call it a draw by mutual chasing. This can be generalized into a rule in two ways:
1) Chasing by protection subversion is a lesser offense than chasing by direct attack. (Just like chasing is a lesser offense than checking.) So there are actually three levels of perpetuals: checking, chasing and unprotecting. Only when both sides do not violate the higher rule, one starts worrying about the next lesser rule. If both sides violate a rule at the same level, it is draw.
2) This is a special exception that must be generalized as little as possible, just as CxR and HxR attacks are explicitly mentioned as exceptions to the rule that you can chase protected pieces, which must not be generalized to think that ExR or AxR attacks on a protected Rook should count as chasing. (However ridiculous it might be that you let the protection make any difference in these cases...) Rule 19 says you cannot chase a Rook pinned by a Horse, even if the opponent counter-chases the pinning Horse. It is some sort of extra protection of Rooks, in particular pinned Rooks.
Take this one:
Code: Select all
9 . . c . . . . . . 8 . . . . . . . . . 7 . . . . . . . . . 6 . R . . . . . . . 5 . . . . . . . . . 4 . . h . . . . . . 3 . . . . . . . . . 2 . . . . . . . . . 1 . . h R . . . . . 0 . . . . K . . . . a b c d e f g h i
The same situation as the Appendix chase, where in this case the moving mounts are white R and black H. But now, at the same time, the black H is chasing the white R.
In interpretation (1), this now should be a win for white, as the chasing of the white Rc6/b6 by direct H attack violates a more important rule than the chasing of Hc1 though subversion of its protection.
In interpretation (2) it would be draw due to mutual chasing, as the subversion of the protection of Hc1 was not a side effect of solving an attack on the Rook that it pinned, and is thus not covered by rule 19.
Now the first example. This is also a bit troublesome, because as it was originally given, it was alternately moving the d- and f-Rooks, with the effect that you alternately chase different Cannons, which is of course always allowed:
Now I took the liberty to replace this by moves of the same Cannon in the PGN file, just interpreting it as one other typo amongst the many in the original document. (The quality is really appalling: diagrams are missing, wrong diagrams are posted, typos in moves...) The fact that a scanned book on Asia rules omits this diagram is also an indication that people discovered at some point there is something wrong with it.Example of Mutual Perpetual Chase
But when only moving the f-Rook, it becomes a non-trivial case again.
Rf6 is a chase. It enables Rd8xi8. That before it could capture that Cannon itself is never an excuse in Asia rules: chases are attacker-specific. It just means that Rf8/f6 cannot be accused of chasing Ci8 on this move, but the other Rook can, and two chasing one is still forbidden. After the move Rd8xi8 has become possible, and no recapture is possible. So chase by Rd8 on Ci8.
Af9-e8 blocks Rd8xi8. So it satisfies the condition that black resolves the chase. As a side effect Ci8 now attacks Rd8.
On the second move Rf8 attacks Ci8 again, and the latter is still unprotected. Black resolves it by protecting it: after Ae8-f9, Rf8xi8 can be refuted by Ca8xi8. So again the three conditions for a chase are satisfied: the capture of an unprotected piece (with this attacker) was not possible before the move, became possible after the move, and became again impossible after the move.
A side effect of Af9 is that Ci8 now attacks Rd8. So this Rook is also chased, alternately by Ca8 and Ci8. Two chasing one is forbidden. (That Ca8xf8 is also made possible by Ae8-f9 has no consequences, as Rf8 is not attacked in the other move.)
What makes this 'corrected' diagram a bit muddy, is that the chase of Ci8 through Rf6 both creates the attack on it (discovering the attack of Rd8), as well as subverts the protection of it. I guess this means it is a violation of both rules. This means that Ci8 is continuously chased by direct attack, though, and not by (possibly lower ranking) protection subversion.
Further note that Ca8 is being chased by Rf6 through protection subversion, despite the fact that both are completely static. The moving of Rf8 and Ae8 as mounts for Ci8 do chase Rd8, but at the same time protect Ca8 from this Rd8. This is the usual situation when you protect a piece by 'X-rays' through an enemy attacker, similat to that in diagrams 39-41. Difference here is that Ca8 is not a Horse pinning Rd8, so that rule 19 does not apply, and that you had a chase by direct attack on Ci8 already, so that it is really immaterial what you do to Ca8.
Of course my initial reaction to this mess was NOT to take it seriously. It was, after all, only an appendix, and it had all the looks of something that was added without thinking it through by a rather incompetent person. And it suited me fine to not recognize chasing by protection subversion as chasing at all. This makes the repeat adjudication in my engine very much simpler, and it never seems to occur anyway...