{"schema":"chessgrammar_motif_entry/1","slug":"interference","name":"Interference","aka":"line-cutting · classic interference","category":{"key":"motif","label":"Direct tactics"},"edition":{"version":"v3.0","year":"2026"},"certified":true,"canonical":"https://chessgrammar.com/motifs/tactics/interference","tabs":{"identity":"https://chessgrammar.com/motifs/tactics/interference#identity","structure":"https://chessgrammar.com/motifs/tactics/interference#structure","examples":"https://chessgrammar.com/motifs/tactics/interference#examples"},"citation":"ChessGrammar (2026). Interference. In: ChessGrammar: A reference for chess concepts, Tactics grammar, edition v3.0. Entry cg:interference@1. https://chessgrammar.com/motifs/tactics/interference","variants":["bishop_line","novotny","pawn","plachutta","queen_line","rook_line"],"seeAlso":["self-interference","deflection","discovered-attack"],"definition":{"id":"cg:interference@1","statement":"A piece is placed on the empty segment of an enemy slider's defensive line and cuts the defender off from the enemy piece it was guarding.","predicate":["Before the move, an enemy slider defends another enemy piece along a rank, file, or diagonal, with nothing standing between them.","The move places a piece on that empty stretch, between the two enemy pieces.","After the move, the defending slider no longer reaches the piece it was guarding, so the guard is cut.","The cut wins material. Under every best defence, capturing the now undefended piece wins more than restoring the guard would concede. A real threat must exist from the start. When the guarded piece is the king, the cut counts only if it leads to checkmate, because a king is never captured."],"diagnosis":"Interference and Pin differ in whose line is occupied. In Interference, a piece enters an enemy defensive line. A pin constrains an enemy piece on the attacker's line. Blocking an enemy line of attack is only a parry. In the counter-example shown here, the defending queen is absent, so there is no defensive line to cut and no Interference.","maturity":{"state":"stable"},"holotype":{"fen":"5r1k/6pp/3RQ3/1p3P2/4Bq2/7P/1b3PK1/8 b - - 0 40","move":"b2e5","san":"Be5","line":["b2e5","d6d5","f4e4"],"interposer":"e5","cut_lines":[["e6","e4"]],"victims":["e4"],"why":"The bishop moves from b2 to e5, onto the e-file between the white queen on e6 and the bishop on e4 that she was defending. The guard is cut. White can reply with Rd5, but the bishop on e4 is still lost, and Qxe4+ takes it with check."},"nearMiss":{"fen":"5r1k/6pp/3R4/1p3P2/4Bq2/7P/1b3PK1/8 b - - 0 40","move":"b2e5","san":"Be5","interposer":"e5","cut_lines":[["e6","e4"]],"victims":["e4"],"why":"The queen on e6 is gone. The bishop still moves to e5, but no guard on the e-file remains to be cut. No line connects an enemy piece to the bishop on e4, so there is no interference.","delta":"The queen on e6, the guard whose line was cut, is removed. Everything else, including the trigger move, is identical.","neighbour":null},"nearMissPending":null,"standing":{"certified":true,"scope":"definition"}},"axes":[{"key":"cut","name":"How many enemy guards the posed piece severs","values":["single","double"],"nature":"partition","note":"Single: exactly one enemy guard is cut -- the base occurrence, not a separate variant. Double: at least two enemy guards are cut by the same posed piece on the same trigger move -- not a name of its own either: every double cut is either Novotny or Plachutta, so 'double' names the shared property those two forms are both instances of, not a third form beside them."},{"key":"double_form","name":"The shared nature of the two severed guards, when cut=double","values":["novotny","plachutta"],"nature":"partition","note":"Novotny: the two cut guards are of different natures (one orthogonal -- rook or queen -- and one diagonal -- bishop or queen). Plachutta: the two cut guards share the same nature (both orthogonal, or both diagonal). Read off the natures of every enemy guard severed by the posed square."},{"key":"guard_line","name":"Which piece owns the defensive line the posed piece severs","values":["rook_line","bishop_line","queen_line"],"nature":"partition","note":"Read on the rear piece of the cut line -- the enemy piece that was doing the guarding. Never the piece being guarded, and never the piece we posed. Every occurrence carries one such line, running from the enemy guard, through our posed piece, to the enemy piece being guarded: this axis names the severed line by the type of the guard that owned it. Because a guard's line is only ever built on a sliding piece, this axis is a total partition of the motif: every classic-interference occurrence carries exactly one of these three values (rook, bishop, or queen line). There is no knight line and no pawn line, and there is no occurrence without a line value."},{"key":"posed_piece","name":"The identity of the piece WE pose on the enemy's guard line","values":["pawn"],"nature":"facts","note":"Read on the screening piece of the cut line, which is our own posed piece by construction. This is the opposite end of the very same relation the guard-line axis reads: the guard-line axis names an enemy piece, this axis names one of ours. Only pawn is named: an earlier 'offensive' value was dropped as a constant that discriminated nothing (the posed piece is always ours), and a king value was deferred for want of any positive reference case. The axis is therefore optional, not a partition: an occurrence whose posed piece is not a pawn simply carries no value on it and keeps only its guard-line value."}],"summary":"Interposing a piece to cut an enemy defensive line."}