The le Grand theme – Part 1

The le Grand theme, named after the Dutch brothers Henk and Piet le Grand who developed it in the 1950s, involves a type of reciprocal change with a paradoxical element. Mostly seen in two-movers, the theme follows this pattern of play: a white try threatens mate A and the black defence x allows mate B, but after the key, mate B becomes the threat and the same defence x leads to mate A. Thus the threat-move and the mating response to a particular black move are interchanged between the try and post-key phases. Unlike the standard reciprocal change of mates, which requires two thematic black defences (e.g. the recent Weekly Problem No.357), the le Grand scheme entails one defence only and hence there is just one main variation per phase. On the plus side, the threat-and-mate reversal is more paradoxical, as the problems below will demonstrate.

Our first illustration has a remarkably early publication date – so early, in fact, that it’s likely that the pattern in question was rendered accidentally. Regardless, this miniature shows the theme as cleanly as most modern examples. The try 1.Sd5? threatens 2.Qg8 [A], and Black defends by playing 1…Kg6 [x], which is answered by 2.Qe8 [B]. But 1…Ke6! defeats the try. The key 1.Bb2! threatens 2.Qe8 [B] instead, and 1…Kg6 [x] again defends, but now 2.Qg8 [A] mates. (By-play: 1…Ke6 2.Qd7.) Inherent to the le Grand theme is a double paradox, which in this example can be described thus: (1) 1…Kg6 disables 2.Qg8 in the try play and yet enables 2.Qg8 in the actual play, and (2) 1…Kg6 enables 2.Qe8 in the try play and yet disables 2.Qe8 in the actual play.

The second problem generates the reciprocal change with intricate strategic effects. The thematic defence 1…cxd3 has a set mate, 2.Qd4, which isn’t part of the main scheme but it represents a bonus change from the subsequent play. The try 1.Rf3? guards d3 to threaten 2.Sa4 [A]. 1…cxd3 [x] defends by removing the knight’s control of b4, but the black pawn has opened the b4-rook’s line to d4 and also pinned itself, admitting 2.Qe1 [B] (not 2.Qd4 due to the activated h8-bishop). The try, however, is refuted by 1…Ra5! The key 1.Rf4! guards d4 to threaten 2.Qe1 [B]. Since 1…cxd3 [x] here doesn’t self-pin the pawn, it counters the threat, but because the pawn has blocked d3 and also opened the f4-rook’s line to b4, the mate is switched to 2.Sa4 [A]. Black has one other defence, 1…Re5, which deactivates the h8-bishop again and permits 2.Qd4. This variation brings back the set mate for 1…cxd3, effecting a mate transference that further enhances the cohesion of the whole composition.

The le Grand theme – Part 2

9 Nov. 2017