|This article uses algebraic notation to describe chess moves.|
It is an example of lines of play being cyclically related: in one phase of play, the Black defences a, b and c are answered by the White mates A, B and C respectively; in another phase, those same defences a, b and c are answered by the White mates B, C and A respectively.
The theme can be understood by reference to the problem to the right: this is the first problem to demonstrate the idea, by Lacny himself (first prize at the Przepiorka Memorial, 1949); it has been much-reproduced. The set play is:
- 1...Nh2 [a] 2.Qd4# [A]
- 1...c1=Q [b] 2.Ng2# [B]
- 1...c3 [c] 2.Qe4# [C]
The key to the solution is 1.Nd2 (threatening 2.Nf1#), after which the mates are changed thus:
- 1...Nh2 [a] 2.Ng2# [B]
- 1...c1=Q [b] 2.Qe4# [C]
- 1...c3 [c] 2.Qd4# [A]
The scheme can be expanded to include more defences; in a fivefold Lacny, for example, the defences a, b, c, d and e are met with the mates A, B, C, D and E respectively in one phase and B, C, D, E and A respectively in another. The cycle can also be extended over three phases to make a complete Lacny cycle; here, the defences a, b and c are answered by the mates A, B and C respectively in one phase; by B, C and A respectively in another; and by C, A and B respectively in a third. This is considerably harder to achieve than the "simple" Lacny, and there are relatively few examples.
In the related threat Lacny, short-cut Lacny or Dombro-Lacny, in one phase A is threatened, and defence b leads to mate B while defence c leads to mate C; in another phase B is threatened and defence b leads to mate C while defence c leads to mate A. Once, problems following this scheme were also called Lacnys, but now a distinction tends to be drawn between the two (Peter Gvozdjak in Cyclone suggests this scheme should be called the Shedey cycle after its originator, Sergei Shedey). There are a number of other themes featuring cyclic play in different phases, including the Kiss and Djurasevic cycles.
- Peter Gvozdjak, Cyclone (Bratislava, 2000) - includes 626 Lacny cycles and 42 complete Lacnys