[Event "?"] [Site "?"] [Date "????.??.??"] [Round "?"] [White "White to play and win"] [Black "?"] [Result "*"] [Annotator "peter"] [SetUp "1"] [FEN "8/3p4/2pB3K/2P1Pk2/p1Pp4/5P2/3P4/8 w - - 0 1"] [PlyCount "9"] [EventDate "1999.??.??"] [SourceVersionDate "2020.04.01"] {[#]} 1. d3 $1 {as we shall see later, this move is essential to trap the Black king} a3 (1... Kf4 2. e6+ {is a straightforward win}) 2. e6 dxe6 (2... a2 3. exd7 a1=Q 4. d8=Q {just leaves White material up and with no particular difficulties in converting}) (2... Kxe6 {this line sets the theme for the puzzle} 3. Kg6 {the Black king is now in a cage} a2 4. f4 a1=Q 5. f5#) 3. Be5 $1 {the hidden idea Christian was referring to.} Kxe5 (3... a2 4. Bxd4 $18) 4. Kg5 {another cage for the Black king, repeating the theme established by the 2. ..Kxe6 line. Without the white pawn on d3 Black could play d3 himself and escape.} a2 5. f4# *