Logical Proca retractor. The main plan fails to Black’s OO# forward defense.
Main plan: -1.Kf6-f5? Se7-g8 -2.Kg7-f6 and 1.Bd7# (pure mate), but this fails on the forward defense -1...Se7-g8 and 1...OO!# Notice that this is the unique reason why the Hauptplan fails: -1…Se7xXg8+
does not defend due to, inter alia, -2.g7-g8=X(+) and forward 1.Bxd7#.
Solution: -1.g2xBh3 g4-g3 -2.Ra2xBc2! Now black can't uncapture anything, because the pawn structure and promoted bishop need 5 captures. -2...Bd1-c2 -3.Bc3xRa5! Ra4-a5 -4.Ke4-f5 Ra5-a4 -5.Kd5-e4 Ra4-a5 -6.Kc4-d5 Ra5-a4 -7.Kb5-c4 Ra4-a5 -8.Kb4-b5 Ra5-a4 -9.Rd2xSa2 Sc1-a2 [Because of this move, the white bishop had to come from c3 on the 3rd move] -10.Kb5-b4 Ra4-a5 -11.Kc4-b5 Ra5-a4 -12.c2xQb3 Qb2-b3 -13.Kd5-c4 Ra4-a5 -14.Ke4-d5 Ra5-a4 -15.Kf5-e4 Ra4-a5 -16.Kf6-f5 [and because of the forward defense Qb2xc3#, the white rook had to go to d2 on the 9th move. Because there are 16 black pieces on the board, the white e-pawn had to promote on e8, so no forward defense OO now!] Se7-g8 -17.Kg7-f6 & 1.Bd7# pure mate.
Notice that: -9.Rc2xSa2 (…) and then -14.Rd2xQc2? fails on account of -14…Sd3-c1+ -15.Kf5-e4 Ra4-a5+ (the bSd3 cannot uncapture) -16.Kf6-f5 Se7-g8+ and Black has the forward defense QxBc3#!
-9.Rc2xSa2 (…) and then -15.Rd2xQc2? fails to -15…Sd3-c1+! and forward Rf4#!
Comments (translated from German): Guenter Weeth: “Compared to the pioneer piece from AF, there are three more constructively impressive uncaptures – and all of that in a highly demanding foreplan – it’s something new. Moreover, what impresses along with the uncapture of a promoted bishop is the exquisitely prepared uncapture of the bQ in the SW corner, which cannot interfere with the return of the wK. Also piquant is the highly subtle refutation of a dual in the event of queen uncapture. It is very difficult to present black forward defense in a defensive retractor. W. Dittmann indicates in Der Blick Zurueck on p. 441 that it appears that the original problem from AF was the only one so far. Therefore, one can state that Nr. 14315 is a delightful, technically optimized and thus new contribution to the implementation of this motif of black forward defense in orthodox defensive retractors.” Klaus Wenda: “After the uncapture of five (!!) black pieces it is proven that the wPe2 promoted on e8 without making captures, so that castling can no longer be performed as a forward defense. The widely scattered and accurately designed uncaptures are impressive. A special subtlety is observed in the 14th move, in the dual avoidance 14.Ra2/Rb2:Qc2? The tries are refuted with a new forward defense by black 1.Qd3# – a delightful double rendition of the thematic motif!” Mario Richter: “An ambitious problem with a rich strategy; several well-hidden and therefore really cunning points require accurate play, so as to achieve the goal of castling prevention.”
