A regular feature of problem gatherings is the quick composing tourney,
where a thematic requirement is set and composers have perhaps a day or
two at most to produce entries. This four-mover shows the quality of
problem that can be produced by two composers of the first rank in a
short time.
1.Ra2 threatens 2.Kb2 and 3.Rxa6 (if 3...S any 4.Sc7).
Most black promotions cannot stop the threat, and for example
1...hxg1Q 2.Kb2 Q+ 3.KxQ forces the black S to unguard c7. Black
however, can defend by underpromoting to a bishop, so that after 2.Kb2 a
move to the sixth rank will cause 3.Rxa6 to deliver stalemate.
White’s response is to confine the bishop’s scope with a
pawn move, so that it can be neutralised on the third move by means of a
capture or pin.
1...h×g1B 2.e3 Bh2/Bf2/Bxe3 3.R×h2/R×f2/Re2 S any 4.Sc7;
1...h1B 2.e4 Bg2/Bf3/Bxe4 3.R×g2/S×f3/Re2 S any 4.Sc7
Two perfectly matched variations. The thematic requirement for the
tourney was to have a pawn promote from the same square to white squared
and black squared bishops. One wonders if the judge downgraded the
problem because the h6 bishop is a promoted pawn.
Jacob Hoover: The seemingly innocuous key 1 Ra2! actually
prepares a threat, namely 2 Kb2 (threat 3 Rxa6 mate) S~ 3 Sc7 mate.
Two main defences exist, and both aim for stalemate, but White has other
plans.