The genre of shortest proof games (SPG) was introduced in the previous article.  Here we will look further into this problem type by considering some lengthier examples with more elaborate ideas.

Many of the popular SPG themes are paradoxical in nature, involving surprising manoeuvres or deceptive diagram positions. Therefore it helps to “expect the unexpected” when dealing with this kind of composition.

And naturally it is also useful to become familiar with these oft-seen themes, so as to know what sorts of effects are achievable in this type.

All of Black’s moves in Problem 104 are visible from the diagram, and their order is strictly determined already, not being affected by White’s play.  Since no captures are involved, it seems that White can play 1.f3, and then simply mark time by shuffling a piece back and forth, e.g. Sh3-g1, for the remainder of the game.

However, such a game would take a single move too long, because the shuffling piece will finish on the wrong square after Black’s final move.

Instead, the solution requires White to make a tempo-losing trek, which is akin to the triangulation manoeuvre familiar in endgames.

The former option would be too slow to be viable, because …exf6 has to be played early to allow Black’s pieces to develop.  So White must have sacrificed an original piece, and promoted to an equivalent one, before the latter moved to its counterpart’s initial square as an impostor.

This is the Pronkin theme, impressively rendered with a knight in one solution, and a bishop in the other.

1.Sc3 Sf6 2.Sd5 Se4 3.Sf6+ exf6 4.b4 Qe7 5.b5 Qa3 6.b6 Bc5 7.bxa7 b6 8.axb8(S) Bb7 9.Sa6 0-0-0 10.Sb4 Rde8 11.Sd5 Re6 12.Sc3 Rd6 13.Sb1; and

If we count the moves required by Black’s pieces to reach their current positions, we find that all of the stipulated fourteen moves are accounted for.  That implies the missing d7-pawn and a8-rook had no time to move and were captured on their initial squares.

Also, Black’s development depends on an early removal of the d7-pawn (to free the queen), a fact that determines White’s starting moves, 1.Sf3 f5 2.Se5 f4 3.Sxd7 f3 4.Sb6 Qd5.

Black must wait for a white knight to return to g1 via h3, before closing the door on that option with …Bh3.  And now if White were to capture the rook with 5.Sxa8, the knight would take too long to get back: 5…Qh5 6.Sb6 g5 7.Sd5 Bg7 8.Sf4 Bc3 9.Sh3 Bxh3??

White apparently has castled queen-side to arrive at position 107, but appearances can be deceiving…

Black needs to promote the a-pawn, shift the new queen to h5, and also capture five white pieces along the way, including the trapped c1-bishop.

These objectives largely dictate White’s play as well for the first half of the game, 1.Sf3 a5 2.Sd4 a4 3.Sb3 axb3 4.a3 Ra4 5.Ra2 bxa2 6.e3 axb1(Q) 7.Bd3 Qxc1 8.0-0 Qxd1 9.Re1 Qh5.