february 24 2015
Yes we Cannes
Course with listeners, spectators, but located 900 km from the speaker.
Let's get back to the good old days: a normal 2# helpmate, with 2 solutions, presented in a "B tournament", but even more interesting than its colleague in the A tournament. It's true, a 2# helpmate with only one solution is a rarity these days. Here is a copy. You won't say I'm overworking you. The 3# helpmate, also single-variant, shouldn't wear you out either. More commitment is required for the 6.5#, but you won't regret it. A nice echo to finish with.
The direct 2#'s are humorous, the 3#'s are perfectly serious. The superb and difficult 4# is one of my best experiences in recent months. The echo presented is prodigious. I got through it just as I was about to "crack". Modules in the hole! To finish, two easy strategies.
Two immediate wins whose common point is obvious (besides the same Black player). The topical ending is a correction of a statement read on a site, both too much and... too little severe! It said that the two players "don't know the classic Vancura draw". Not quite... Besides, good defence requires a return of the TB (switchbaaack, said a great retired French problemist) not initially foreseen by the speaker.
The study of the day is based on a curious ZZ, but nevertheless very accessible. A virtual technical phase is more complex, but fortunately optional.
The day's game is of the kind that demonstrates the extraordinary value of our art, in the face of spasms of history.
And, ipso facto, its immortality. The listeners proposed 16...g6 17 Rb1! Qa5, whereupon the speaker failed to reply the ingenious confinement of the bQ by the monster: 18 Rb5! Qxc3 19 Bb2. Moreover, 20...Bxe6 21 Ng5 Nc6?! is, in spite of the howling of the said monster, much more difficult to refute than expected. Moreover, we could easily have spent two more hours on this game, let's just mention the two incredibly rich continuations we had to skip: 20...Bxe6 21 Ng5 Bb3! and 20...Bxe6 21 Ng5 Qxa3, sub-variant 24...Qa6+.
A fairy part on a theme now familiar to St. Lazarians, "Growing Men" chess. Note: Ronald Turnbull's commentary on this problem is excellent, contrary to a widespread habit in (even few good) reviews. But it is in the style of what I have tried to do, by necessity, in my Endings: it is the minimum to access understanding, requiring a more or less important effort of reflection from the reader. It is possible, with more space and time, to develop further, exactly as in my book "Les Finales" (version to come), and thus to be better understood.
And a few others from the bestiary, translated into Chessbasist language as best as possible.
See you, God willing, at... an unknown date.
Have a good time.
Fairy
Daniel's word on retrograde analysis in Growing Men
Chess is a domain where, as for many others, access to beauty is open to all but requires a sometimes important initiation phase.
In the case of fairy chess which the Master has popularised for more than 30 years, for each new genre he has always taken care to present first "elementary" problems perfectly didactic even if they could be without interest for the expert.
As the audience of the course has long since become familiar with the basics of enchantment, the Master proposes problems that are as beautiful as they are exciting, but more elaborate.
So far, nothing but the obvious in what I have said. They describe the classic situation of "face-to-face" sessions where the speaker can adapt his or her speech to the level of the audience present in the room.
The problem becomes more complicated in this new course given by videoconference and directly published on this site. The occasional walker will still be able to find his way in the "classical" chess (at the price of more or less efforts).
On the other hand, the fairy part, to remain interesting, must be adapted to the level of the reader (or at least compatible with it). The Master has therefore chosen problems that are accessible to the usual audience (if not findable by them!). This is what we find in the now classic part "Master's diagrams".
Alas, inevitably, Turnbull's very pure and admirable problem is bound to discourage and even disgust the uninformed reader. This would be just as bad for the false idea that he will have of enchantment as for himself, who would thus miss the opportunity to discover all the interest of the genre and even, I dare say, its accessibility!
I will therefore take advantage of this textual part, which is left to the freedom of the clerk, to try to make this problem accessible to any willing and curious reader who has not been able to take advantage of the indispensable introductory phases I mentioned above.
Growing Men : once a piece has made a move, it can no longer make a move of shorter length. Thus, it can then play moves of the same or greater length, knowing that as soon as it plays a move of greater length, this becomes the new basic measure below which moves are no longer permitted.
Of course, since legal moves here are more conditioned by the past than elsewhere, it is easy to imagine that retrograde analysis will not be absent.
Simplified principles of retrograde analysis:
Rule 1) Any information about the past that can be proven can (and should) be used.
Rule 2) Any move that cannot be shown to be illegal is presumed to be legal. Or again: that which cannot be shown to be prohibited is authorised.
Illustrations in Growing Men :
W: Kh1 B: Be4. Black to move. What is Black playing? ?
Point 1) This position being given B to move, we deduce that Kh1 is not in check.
This means that Be4 is not allowed to make Bxh1 and therefore his previous move had a length of more than 3 B-steps.
His only legal move is therefore Ba8 which now makes check.
Point 2) If the wK has arrived at h1 via g2, then he is condemned to play moves of length 1.4 (root of 2 to be precise since it is a move that runs along the diagonal of a square of side 1. In this case, everyone knows that the diagonal is longer than the side).
And then B can announce mate by playing Fa8 because they attack the h1 and g2 squares and wK is not allowed to play on g1 or h2 since these moves would be shorter than his previous movet.
However, the W's are not mated because the position does not allow to prove that they did not arrive in h1 by g1 or h2.
To summarize: in point 1, according to rule 1, we prove that Ba8 is the only move, so it must be played.
In point 2, according to rule 2, we cannot forbid Kg1 or Kh2, one of them can (and even must in the circumstances) be played.
Let's move on to the piece de choix, the problem itself.
R. Turnbull
Growing Men. W's play and mate in 6 moves.
A) Consider the bP h2.
The presence of the h7 bP shows that this h2 pawn is not the Ph. It thus comes from one of the files (from c to g, it doesn't matter) knowing that it made at least one capture at a time (to change file) and that from this moment, all its movements were only captures, the moves of normal march having become illegal because too short.
All this to conclude that he must have passed through g3 !
In the aftermath, we have the following thought: which piece played the last B move ?
Compulsorily K because if it had been P, as it has just been established that it passed through g3, Kf2 would have been in check.
B) Let us continue our progress in the knowledge of the past.
We have established that the last B move was Kh1, but from which square did the K?
If it came from g1, then it would have been double-checked by the K and the R which, whatever their pasts, would have had the right to play Kxg1 and Rxg1 respectively since these are moves of maximum length for each of these two pieces !
Well, cheer up, this point is soon to be eclipsed. If the last move was Kg1-h1, the last W move (making double check) was necessarily Kg3-f2... which is not possible because the wK would have been in check by the bK.
Conclusion, the last B move is Kg2-h1.
To avoid periphrasis, we will now say that the bK is "enlarged" to say that he is now condemned to play diagonal moves.
This kind of exercise is quite exciting because it develops the rigour of advanced reasoning in a more accessible medium than mathematics. This reason should be enough to put retrograde analysis in school activities, but I digress.
By the way, since we are talking about logical reasoning, the reader will have noticed that I have skipped a step.
I have shown that Kg1-h1 was not the last move, but this does not allow us to conclude completely that the last move was Kg2-h1: for this, we must be able to legally obtain the position with the bK on g2 and the wK on f2, Black to move.
This will be the subject of the next point.
So far we have used Rule 1 to establish certainties. We now need to use Rule 2 to establish the different possibilities that are open to us.
C) What was the last W move, or more precisely what were the last possible White moves, to obtain the position (knowing that the last B move is Kg2-h1) ?
A first solution (the simplest) is to say that the wK was already enlarged. In which case, it was enough that he was in g3 (not in check and not in check either!) since both R's are enlarged. The W's then play Kg3-f2 (still not in check with their K and whether or not they are in check with their R is unknown) and the B's answer Kg2-h1. The position is reconstituted and legal. But this does not suit us, because an enlarged wK controls less than twice as many squares, and we have to checkmate.
Is there another way to legally obtain this position without having an enlarged wK?
Yes, by saying that the last W move is Ke2-f2 (thus defeating Kg2). Note of course that this immediately implies that the wR is already enlarged to the maximum (moves of length 8 obligatory) because to be able to play Ke2-f2 the Rg8 must not check Kg2.
In conclusion : We can therefore either have a totally free R but at the cost of an enlarged K, or an K in full possession of its means but at the cost of an enlarged R.
We have completed the retrograde analysis phase. It only remains to look for the solution of this direct mate in 6 moves.
There are two ways of looking for it:
Either wR is unconstrained and can go to checkmate a1 ... but then wK is enlarged and the Bs can flee via Kg2!
Or wK controls g2 ... but R is condemned to moves of length 8. It is not obvious, but this is the solution !
To continue learning while taking a breather, here is an imaginary dialogue between the Master and a passing visitor who has now assimilated the rules but is not yet used to their implementation .
-The passerby: Goodness, but it is obvious ! I even demolished the problem: there is mate in 2 moves by 1:Rg1+ hxg1= anything 2:Kxg1 mate".
- The Master : Bravo. (yes, he always starts like that the Master, he encourages, but you always have to wait for the continuation!). But a remark if you allow. If the Ws play Kxg1 they are enlarged and no longer control g2 !
- The passer-by : Indeed. Thank you, Master, but never mind. I still demolished taking into account your remark.
It will simply capture me one more hit. 1:Kf1!!! (to control g1 without enlarging the K!) 1:...b6 2:Rg1+ hxg1= anything 3:Kxg1 mate.
- The Master: Bravo! You are attentive and you know how to react. But one remark if I may.
We are in a direct mate, not in an helpmate. Thus, on your move 2:Rxg1 I suggest playing b6-b5! as I could not fear this ridiculous R just able to return from where it comes since it is enlarged !
- the passer-by :...
Here the report stops because he insulted Turnbull, which cannot be tolerated.
Obviously, all this is not trivial and has a bearing on the following solution.
When you have convinced yourself (it is difficult!) that the R cannot mate, you say to yourself that you must mate with the K. But Kf1-g1 does not mate because Kg1 is prohibited by the Ph2.
It is thus necessary to make its counterpart with Kxh2... without ever enlarging the wK because that would allow the B to play Kg2!
The solution seems to be very simple with a mate in 4 moves: Kf2-f3-g3-h3!-h2 mate.
Where is the last finesse? The reader who has had the courage to last until now should capture a minute to answer this question.
1:Kf3?! b5! 2:Kg3 ... draw! because the B's are stalemated ! (the reader is now expert enough to understand).
Holy Turnbull !!
Hence the solution, which is now clear. 1:Kf1!! (not to prove that the K is not enlarged, there is no need to prove this here since it is one of the legal possibilities as has been shown, but to prevent the defence by pat, which is a much finer and thematic justification of this key).
1:.. b6 (because, as the passer-by had sensed, 1:...b5? 2:Rg1! True, Rg1 does not checkmate but it offers the N's a move as forced as it is unfortunate 2:...hxg1 3:Kxg1 mate)
2:Kf2 b5 3:Kf3! b4 4:Kg3 b3 5:Kh3! b2 6:Kxh2 mate. Since Rg8 plays no role in the mate board.
Click in the right part of the chessboard to move forward, left to move backward... or directly on the move in the solution
#6 Growing Men
hs#3 Kobul Kings
b) bPb6-->f4
hs=5 Kobul Kings
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