in der Retroanalyse
20 - Dr. Niels Høeg
Die Schwalbe, 1933
10+11. Matt in 3 Zügen
Here, castlings are mutually exclusive. To see this assume, by way
of contradiction, that both sides may castle. Then wQ and wQR have been
captured by bNs (together with the wQB) and wQf4 is the promoted wPf2
on c8 or b8. So that bl. caps f7xg6, b7xa6, e7xd6 consumed the 2 wNs
and the wBf1. There are now three cases:
Mate in 3 is with 1. Qxd6!! (threat. 2. Rf1 & 3.
Rf8#) Bb7 2. O-O !! (not 2. Rf1 ??) forbidding the
now-illegal defense 2 ... O-O-O??, and allowing 3. Rf8#.
Solution by Philippe Schnoebelen