[Retros] The generic understanding of Retro-Strategy: fairy chess

[Valery Liskovets]

Dear retro-fans,

In orthodox retro-composition, the retro-strategic post factum
(= PF = subordination) logic results in contests related to mutually
incompatible W's and B's castlings, or, possibly, in different
incompatible elements, as Guus Rol spectacularly showed in his
recent #7 problem. But as he noted, "The most important reason
for discussing retro-strategy is the bearing it has on fairy chess
variants...". Fairy genres are indeed fruitful for retro-strategy.
In particular, pieces retro-volages, which demonstrate absolutely
NEW possibilities of the post factum logic, which aren't, perhaps,
widely known. Let me show a simple old example.

V.Liskovets and N.Plaksin, feenschach, h.81, 1986
W: Kg1 Rb5 Rf3 Sb1 Sc3 Pd3;
B: Ke1 Rd2 Rf2 Pc4
 _________________

| _ : _ : _ : _ : |

| : _ : _ : _ : _ |

| _ : _ : _ : _ : |

| : R : _ : _ : _ |

| _ : p : _ : _ : |

| : _ S P : R : _ |

| _ : _ r _ r _ : |

| : S : _ k _ K _ |

|_________________|

#2   b) pRA     6+4
Pieces retro-volages

Here at least one wR is normal (recolored from a bR) since it
could not be promoted and come from the 8th rank stepping on light
squares only. However, by the general retro-volages presumption
(any piece is considered to be volage unless the opposite can be
proved), one wR is definitely volage (it is the original Rh1).
The same for the bRs.

a) (PF implicitly) By the retro-strategic logic (naturally spread
to this fairy genre), the hidden nature of the 4 rooks, which is
uncertain in advance, is subject to specification in the course of
the game: the FIRST wR and first bR that change the color of their
square are declared to be volage and have to immediately turn into
enemy's R, e.g., 1.Re3/Re5=bR. Now, the solution is the following:
   1.Rb2=bR! - 2.Re3(=wR!)#! (2... Rde2=wR??/Rfe2=wR??).

Two unusual kinds of contest (or, sooner, cooperation in the first case)
take place here: positive (MAKING NORMALITY LEGAL) and negative
(FAILING). Both are concerned with rooks of the SAME color.
The keymove intentionally specifies the moving wR as volage and
thereby makes the second wR normal. On the other hand, because of
illegal auto-checks, none bR can screen bK, as if they both would
have been volage: failing immediately (a Buridan-ass-like paradox)!
Besides, similarly to W, Black can undertake recoloring manoeuvers
that make his second R normal and, thus, prevent from the mate Re3.
But, instead, White mates by his newly appeared Rook:
   1... Rdc2=wR/Rxd3=wR/Rxf3(Rg2)=wR 2.Rc1#/Rd1#/Rf1#.
These lines explain the thematic try
   1.Rb4=bR? Ra2=wR! 2.Re3(=wR)/Re2+ Rf(x)e2(=bR)!

In fact, the second paradox is known in orthodox chess due to the
remarkable (and unique) study by G.Rinder, Die Schwalbe, h.35, 1975:
W: Kf5 Pc7 Pd5 Pe3 Pe4 Pf6 Pg4 Ph5;
B: Kh6 Bc8 Pb7 Pd6 Pd7 Pe5 Pf2 Pf7 Pg5 Ph7; =.

b) By the opposite pRA logic, there are 4 retro-variants (RVs)
known in advance and 4 corresponding partial solutions. The latter
contain W's moves without recoloring. E.g., if Rf3 and Rf2 are
(known to be) volage (hence Rb5 and Rd2 are normal), then
   1.Re5(=wR)+ Rde2(=bR) 2.Rxe2#!

Such new controversial opportunities are most attractive for me in
fairy chess (although I'd never composed myself in fairy genres
other than retro-volages).

Valery Liskovets
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