Many retros have the "Mate in one" stipulation. How
can this be a real problem?
With such problems, the direct (i.e. forward) stipulation
is generally an implicit way of asking for a retrograde analysis of
the position. Of course this is only interesting if the actual solution
cannot be found without a correct analysis of the past of the position.
This is the case when the solution involves
castling or an en passant capture.
But often the trap is that RA will establish that Black has the move.
Then the intended direct mate may be performed by Black (1st
situation). It may also be performed by White against any Black
1st move (2nd situation). In any case, the real interest
of the problem is usually its retro-analytical content, and the mate
in one is the icing of the cake. Some problems explicitly use the "Mate
in 1 (Who?)" stipulation, to make sure that
solvers won't miss the real point.
Because of the trap intended by the composer, it is most appreciated
when the direct stipulation is the simplest possible, e.g. "mate in
one!" (see also problems without words).
That way, lemmings are sure to make a fool
Here is a simple example of the 1st situation:
diagrammes 60, 01/1983
15+15. Mate in 1
And a simple example of the 2nd situation:
W. F. von Holzhausen
Akademische Schachblätter, 1901
5+2. Mate in 1