The Retrograde Analysis Corner

Miscellaneous Problems

Solution

W. Langstaff
The Chess Amateur, 1922

[4k2r/8/5B1P/3R1KpP/8888]

5+3. (RV) Mate in 2

Analysis: If Black's O-O is still legal, then his last move was 0 .. g7-g5 and an en passant capture is legal. Following the PRA stipulation, we consider the two possibilities in turn.

Solution:

Black may castle. Then 1. hg6 ep! is legal. White follows with 2. Rd8# or, if 1 ... O-O, with 2. h7#.
Black is not allowed to castle. Then 1. Ke6! is followed by 2. Rd8#.