The Retrograde Analysis Corner
Solutions
Nenad Petrovic The Problemist, 1930
16+13. Who mates in 1?
Wh. caps are axPb, cxd and f4xe5. For balance, bPf7 was promoted on f1. Position unlocks with a very precise unpinning maneuver. Retract -1. Rf3-d3 h4-h3 -2. Rf6-f3 h5-h4 -3. Rd6-f6 h6-h5 -4. Rd5-d6 h7-h6 -5. Nb4-a2 Nc3-a2+ -6. Nc3-a4+ Bb5-a4+ -7. Rb5-d5+ Bc5-b6 -8. Qb6-a6 and everything unlocks.
Necessarily, Bl. has the move in the diagram position (and indeed last 15 single moves are completely determined). Therefore, mate in 1 is with 1 ... Qxa2# !! and not the illegal 1. Rcxc3#??
