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What if a pawn could “promote” to a pawn?

What if a pawn could “promote” to a pawn?

Rocky64
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A pawn must be replaced by a piece upon reaching the eighth rank, but suppose it is legal for the unit to remain as a pawn, one that becomes immobile. Are there situations where such a non-promotion move would be the best possible, i.e. the only move to force a draw or even a win? The question was answered in the affirmative back in the 19th century, when the pawn promotion rule was in dispute. An endgame study by Kling and Horwitz was cited by Steinitz to demonstrate how a pawn “promoting” to a pawn (abbreviated as “P=P” below) could uniquely salvage a draw, by facilitating stalemate. Since that time, problem composers have continued to explore this paradoxical idea – a sort of ultimate in underpromotion – in a variety of ways. One angle is to construct the most economical version of such a “Draw” problem. Another challenge is the “Win” study itself, a position where non-promoting is the sole winning move; this more difficult task has only been accomplished relatively recently.

Drawing by P=P

“Economy of force” is a basic principle of chess composition – it holds that for a presented theme, we should minimise both the number of pieces used and their ranks. In the case of a “Draw” study solved by a P=P move, the fewest number of pieces required seems to be six, as realised by several problems. The economy record is hence focused on lowering the ranks of the six units deployed. Our first two selections, which involve very different schemes, represent the best efforts along these lines.

After the thematic try 1.h8=Q?, the tempting 1…Bf3? allows White to escape with 2.Qa8! (e.g. 2…Nh4+ 3.Qxf3+ Nxf3=, or 2…Kf2 3.Qa2+). Only 1…Nf4! wins; it shields the king from checks on the f-file while threatening both 2…Bf3 and 2…g2+ 3.Kh2 g1=Q. For example, 2.Qa8 g2+ 3.Qxg2+ Nxg2, or 2.Qh3+ g2+! 3.Kh2 Nxh3 4.Kxh3 g1=Q. White must aim for stalemate with 1.h8=P! Unlike other economical studies showing the theme, here Black is able to release White with 1…Ke2/Ke1; yet White still manages to draw: 2.Kxg2 followed by 3.Kxg3. The post-key play accentuates the paradox: an active white queen would face defeat but the lone white king saves the day.

Andrew’s position contains terrific try play. 1.g8=Q? g1=Q! – Black sacrifices both major pieces – 2.Qxg1 Rf8+! 3.Qg8 Rxg8+ 4.Kxg8 Kg6!, or 2.Qxf7 Qd4+ 3.Kg8 Qd8+ 4.Qf8+ Qxf8+! 5.Kxf8 and the h-pawn carries the day. Black is also unfazed by five white queen checks, in contrast to most miniature settings of P=P where Black aims to preclude such defences. Here Black meets each check with either an immediate mate or a capture that avoids stalemate: 2.Qf8+ Rxf8, 2.Qg7+ Qxg7, 2.Qxh7+ Rxh7, 2.Qg5+ Kxg5, or 2.Qg6+ Kxg6/hxg6. There’s no such stalemate avoidance though after 1.g8=P!

The next “Draw” problem doubles the theme: at the cost of just two more units, we create a position that is solved by consecutive P=P moves.

The try 1.g8=Q? threatens 2.Qg6+/Qg5+, inducing stalemate; thus 1…b1=Q? is ineffective. Black’s only winning move is 1…Nf4! Now that 2.Qg6+ is countered by a knight mate, and 2.Qg5+ Kxg5 isn’t stalemate, White cannot stop Black from winning on material, e.g. 2.Qg7+ Kh5 3.Qxf6 b1=Q 4.Kg7 Qb7+ 5.Qf7+ Qxf7+ 6.Kxf7 Bxh7, or 2.Qf8+ Kg5 3.Qh6+ Kg4! 4.Qh1 b1=Q. The key 1.g8=P! threatens stalemate, which must be relieved by 1…Nxg8. Remarkably, 2.hxg8=Q? is not defeated by 2…b1=Q?, because 3.Qxe6+! Bxe6 prompts another stalemate (also 2…Nd4? 3.Qg7+ Kh5 4.Qxd4 draws). Instead, the unique 2…Kh5! uncages the white king and neutralises the queen’s sacrificial threat. The white queen is left incapable of picking off either minor piece or the unprotected pawn, e.g. 3.Qe8+ Kg4 4.Qa4+ Kg5! 5.Qb4 b1=Q, or 3.Qf7+ Kg4 4.Qg8+ Kh4 5.Qg1 b1=Q and Black wins. Only 2.hxg8=P! salvages the draw.

Winning by P=P

A study position in which White can win only by executing a non-promotion is much harder to construct. What could be the decisive advantage of a P=P move over all normal promotions? The only answer seems to be that other choices of promoted pieces would result in Black compelling White to use these different pieces to stalemate Black. I devised a rendition of such a “Win” study with this strategy a few years ago, on the Chess.com forum. Unbeknownst to me, two decades prior another composer, John Beasley, had tackled the theme successfully. Our two positions make an interesting comparison, and I have to admit that John’s has slightly better construction and play!

White has overwhelming material advantage but must begin with a capture of the checking rook, after which Black aims to sacrifice the queen to create stalemate. 1.exf8=Q? or 1.exf8=B? places an extra guard on d6 and enables Black to divert the d5-queen with 1…Qg8+! 2.Qdxg8= (or any other capture on g8), leaving the black king unmovable. Similarly, 1.exf8=R? adds an attack on d8 and allows the f6-bishop to be deflected: 1…Qg7+! 2.Bxg7=. And if 1.exf8=N? controlling d7, that effectively releases the f5-bishop: 1…Qh7+! 2.Bxh7=. Only 1.exf8=P! wins, evading all the stalemate traps. 1…Qg8+ 2.Qxg8 Kxd6, 1…Qg7+ 2.Bxg7 Kd8, and 1…Qh7+ 2.Bxh7 Kd7. Problem aesthetics would regard White’s key-move capturing a rook as over-aggressive, but that’s more than justified by the exceptional idea achieved.

My version also resorts to a piece-capturing key, though it avoids the unsubtlety of starting with White in check. The black queen is threatening mates on a8 and f7, severely limiting White’s options. 1.exf8=Q? or 1.exf8=R? pins the knight and stalemates Black immediately. 1.exf8=B? guards g7 and allows Black to deflect the f5-knight with 1…Ne7+! 2.Nxe7= (or 2.Bxe7=). 1.exf8=N? controls h7, which means Black can eliminate the f6-knight with 1…Nxf6+! 2.gxf6=. If White tries 1.e8=Q?, Black still draws with 1…Qxf7+ 2.Qxf7 Ne7+ 3.Qxe7= (or 3.Nxe7=). The unique 1.exf8=P! thwarts all stalemate attempts. 1…Ne7+ 2.Nxe7 Kg7 or 1…Nh6 2.Nxh6 Kg7. Best for Black is 1…Nxf6+ but after 2.gxf6 Kh7, White is still a piece ahead and so wins the ending easily.