In Proca Retractor compositions the main challenge is to find good motivations in order to force Black to retract the en passant capture. This challenging theme can be realized combined with different fairy conditions.
Proca Retractor definition:
A Proca Retractor is a defensive Retractor. Black is defending by trying to retract the moves that will forbid (or delay) the achievement of White's goal. You may see at the Retro Corner an example by W. Dittmann of orthodox Proca Retractor showing two en passant captures.
The first composer who successfully showed the Black and White double en passant capture was Dr. Klaus Wenda. In the first two problems we can see how he managed to present this theme combined with Madrasi and AntiCirce Cheylan.
Madrasi: Madrasi Chess is a fairy variant of chess where units (King excepted) are paralyzed when attacked by an enemy unit of the same nature. A paralyzed unit cannot move and does not give check ("Checks are fairy"). It can only paralyze enemy pieces, including its own paralyzer.
1.g5xf6 e.p. f7-f5 2.Qf3-a8 g7-g6 3.a5xb6 e.p. b7-b5 4.Qe3xpf3 e4xf3 e.p. 5.f2-f4 e5-e4 6.Qc1xpe3 d4xe3 e.p. 7.e2-e4 d5-d4 8.Qe3xRc1 [8…d6-d5 possible]
& 1.Qb3+ Kxb1#
Black pawns can’t shift on the free columns without uncapturing a white piece. Since all white figures are present on the board, only pawns can be uncaptured. Under Madrasi rules, uncapture of a pawn by a pawn is possible only by using the en passant trick.
The second en passant capture is needed in order to provide Black an extra tempo playable before the forward play. This explains also why white pawn must be placed on a5 instead of c5.
Anticirce Cheylan: the capturing piece disappears and is immediately reborn on its home square while the captured piece is removed for good. The capture is not legal if the rebirth square is not free. A pawn capturing on the eighth rank is first promoted and then reborn on the home square of the promoted man. Here "checks are fairy" i.e. a King is not in check if its "capture" is not legal because the rebirth is not possible. A piece is not allowed to capture on its home square.
1.a5xb6 e.p.[>b2] b7-b5 2.Kc5xSb6 [>Ke1] c4xb3 e.p.[>b7] 3.b2-b4 Qf8-f5+ 4.f5xe6 e.p.[>e2] e7-e5
5.Kd5-c5 d4xe3 e.p.[>e7] 6.e2-e4 Sc8-b6+ 7.Bf7-g8
The most often met motivation of black en passant capture is a double check. White King must arrive on d5, but first the black Queen must be decoyed from controlling this square.
Once the white King arrives on d5 the check delivered by bBf3 must be parried, hence the need to uncapture bSb6, as the other possibility 6…Kc8-d7 is ruled out by the presence of bPc6.
The whole sequence has a logical character, as White needs to block the flight c8 in order to be able to mate.
Inspired by these masterpieces of Austrian Grandmaster, the Romanian composers tried also their hand using other genres: Immun Chess and Circe Assassin.
Immun Chess: a piece cannot be captured if its Circe rebirth square is occupied.
Crişan, Vlaicu & Răican, Paul
Christmas Tourney France-Echecs, 2009
1.h5xg6 e.p. g7-g5 2.Kd3xpe3 f4xe3 e.p. 3.e2-e4+ f5-f4+ 4.a5xb6 e.p. b7-b5 5.Ke3xpd3 c4xd3 e.p. 6.d2-d4 c5-c4+
7.b3-b4 & 1.Sb4#
White aims to play -1.b3-b4? & 1.Sb4#, but at the moment there are flights d6, e6 and c5.
The fore-plan consists in immunizing pawns d6 and e6 and less specifically to block c5. The model mate also makes use of immunization of wSb4 by bSg1.
The trick used to force the en passant retraction is a simple check by a immobilized black Bishop.
Circe Assassin: the captured unit is reborn on its rebirth square even if the rebirth square is occupied. And then the occupying unit disappears for good. Hence a unit on its home square cannot be removed.
1.d5xe6 e.p.(e7) e7-e5 2.Kd2xpe3(e7, -wBe7)
f4xe3 e.p.(e2) 3.e2-e4 Re4xpe2(e2, -bRe2) 4.Kc2-d2 Rb1-c1+ 5.Kb3-c2 a5-a4+ 6.c5xb6 e.p.(b7) b7-b5 7.Kc2xpb3(b7, -bBb7) a4xb3 e.p.(b2)
8.b2-b4 Rb4xpb2(b2, -bRb2) 9.Sb5-d4
& 1.Rxb1(Ra8) Rxb5(Sb1, -wRb1)#
Again Black en passant captures are forced due to specific double checks, immediately followed by active suicides of black Rooks.
The whole purpose of the play is to leave a white Bishop e7, ensuring the control of c1 thanks to bRe4, and a black Bishop b7 preventing the advance of wPc5 in the final position.
Please note that leaving a black Queen b7 would thwart the intention, as black would be able to move in the forward play 1...Qxb5(Sb1, -wRb1) and no mate as 2.Qxb5(Qd8) is playable.
Let’s hope new examples will occur in the future.