threat anti-reversal
The order of a key and a threat cannot be reversed between two phases.
Scheme:
1.A ~ 2.B
1.B ~ 2.A??
cyclic threat anti-reversal
Three White moves occur in three phases in cyclical pairs: a key and a threat.
Scheme:
1.A ~ 2.B
1.B ~ 2.C
1.C ~ 2.A
Sanders, Ivor L.
The Problemist, 1993
mate in 2 moves
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