Plachutta
The Plachutta is a device found in chess problems wherein a piece is sacrificially positioned in blockade to deny coverage of multiple distant squares required by the opposition. For example, two of an opponent's bishops, queen, or rooks are defending locations through an intersection square, and an enemy unit moved into that square blocks disrupts coverage in such a way that, even if captured, the previous defensive situation cannot be restored. The Plachutta is named after Joseph Plachutta (1827–1883), and related to a number of other problem themes: it can be regarded as a Würzburg–Plachutta brought about by a sacrifice on the critical square (a Würzburg-Plachutta itself being a pair of Holzhausen interferences); or it can be thought of as a Novotny with similarly moving (rather than differently moving) black pieces involved (a Novotny itself being a Grimshaw brought about by a white sacrifice on the critical square). It can also be compared to the anti-Bristol, in which two similarly moving black pieces interfere with each other along the same line. Examples 1. The problem to the right is a relatively simple example by William Shinkman, published in White Rooks, 1910. It is a mate in three (white moves first