Note: The Forsythe notation for the position is included underneath the diagram to facilitate setting the position up in your own PGN viewer. (Most chess programs have the ability to load FEN directly or cut & paste FEN notation into a blank board.)

1b6/4P3/1P2PN2/8/8/P1k5/P1p2P2/K5B1 w

1.Ne4+ (1.Nd5+ won't do since Black simply replies 1...Kd2 and the c pawn Queens. One possible continuation is 1... Kd2 2.Kb2 c1=Q+ 3.Kb3 Qc2+ 4.Kb4 Qc6 and Black wins rather easily. And, of course, any other move by White other than 2.Kb2 after 1.Nd5+ loses instantly to 2... c1=Q++.)

1...Kd3 2.Nc5+ Kc3 3.Nb3

This knight now covers the Queening square.
So far, so good, however...

3...Be5.

4.f4. Attacking the Bishop. (Note that Bh2 won't do as Black then mates in 7 beginning with Bf6.) 4...Bg7 (Black keeps the Bishop on the diagonal since if 4... Bxf4 then 5.Bd4+ and White is out of trouble.)

5.e8=N! The only move! White under-promotes to a Knight, attacking the Bishop!

5...Bh8 6.f5 Again, the only move! Black was still threatening to mate beginning with 6...Kd3+. Now White can block the diagonal with 7.f6.

6...Be5

7.Bh2 Bxh2 8.b7 Be5 (Renewing the threat.) 9. b8=B! A second under-promotion, this time to a Bishop! It's the only move since if White promotes to a Queen Black can draw with 9.b8=Q Kc4+ 10.Qxe5 c1=Q+ 11.Nxc1 stalemate!

9...Bxb8

12.e8=R! A third under-promotion, this time to a Rook!! Again it is the only move, since a stalemate would again occur after 12.e8=Q Kc4+ 13.Qxe5 c1=Q+ Nxc1.

12...Bf6 13.Re6 Bg7 14.f6 and White wins! The Bishop's diagonal is finally blocked for good!