Plachutta

The Plachutta is an interference theme involving two same-color pieces that defend along crossing lines. Both use similar line movement in the mechanism, such as a rook and queen acting along rows or columns.

White sacrifices a unit on the intersection square. If one defender captures it, that defender occupies the crossing and closes the other defender's line. If the second defender captures, the reverse occurs. White obtains a different continuation according to which line has been interfered with.

1. First identify two defensive lines that cross.
2. A White unit is sacrificed exactly at their intersection.
3. Either capture removes the sacrifice but obstructs the other defender's line.
4. White exploits the defense that has been disconnected.

The defenders need not be identical pieces. What matters is that they share the type of line movement used by the mechanism. In the complete form, the piece that will be interfered with first makes a critical move, crossing the future intersection square and preparing the later effect.