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In each problem white is playing up the board and is to play and force mate in the number of moves stipulated. For the ‘mates in 2’ the solver need only submit White’s first move – the ‘key’. For the longer problems, the key and all variations of full-length are required, but only up to White’s penultimate move. To save reams of writing, include any threats that non-checking white moves may carry. After such a threat or threats only black moves that defeat it or them need be given. A threat is defined as how White would accomplish the stipulation if Black were to miss his next move. Only full-length threats need be given and no black moves at any point that lead to mate in fewer than the number of moves stipulated need be given. Some threats can be ‘virtual’. This means that all black moves defeat the threat, which means that White never needs to carry out the threat to achieve the stipulation. Such virtual threats need not be given and won’t be awarded points. An example ’mate in 3’ and its model solution follows. All in bold is required for full points.

Peter F Copping

1st Prize, The Observer, 1958

Mate in 3

1.Sa3!   [2.Sc2       (3.Sc1,Sd4#)
                 c3    3.Bd5#]

1...Rf5   2.Bxe4 &     3.Bc2#
1...Rf6   2.Bd5  &     3.Bxc4#)
1...Bg7   2.Bxd6      (3.Sc1#)
                 Bxb2+ 3.Rxb2#
1...e3,f5 2.Bxd6 &     3.Sc1#
1...f6    2.Rc2  &     3.Rc3#

These rules are in accordance with those in use at FIDE regulated chess solving events.