en passant checkmate
Do you see all the variations?
After the first move, if Black moves either rook, White can checkmate with a queen on the very next move.
After the first move, if Black moves either pawn one or two squares, White can checkmate with a capture of the pawn with the e
(en passant, in some cases) on the very next move.
After the first move, if Black moves his king, White can checkmate him with a queen thanks to the two pins and the bishop support!
Nicely built mate in two Zugzwang
!
Very good! You found the variations. Now the tries. What after 1. e6?, 1.Be6? 1.Kd5?, 1.Kc5? 1. Qd5?
Note there is also "set play" (what black could do in the diagram if he were on move). Both black check optons are met by white checkmates but no longer after some of the tries! Not luck but carefully programmed!