Lacny


The Lacny or Lacny cycle is a chess problem theme named after Ľudovít Lačný, the first person to demonstrate the idea in 1949.
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 ; it has been much-reproduced. The set play is:
The key to the solution is 1.Nd2, after which the mates are changed thus:
As well as in set play the theme can be shown in tries, more than one solution or twins.
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. There are a number of other themes featuring cyclic play in different phases, including the Kiss and Djurasevic cycles.