Interference
Placing a piece between two coordinated enemy pieces, breaking their cooperation.
Interference happens when one piece is dropped between two enemy pieces that were working together on a single line. The intruder separates them — the back piece can no longer defend the front piece, or the two long-range pieces can no longer support each other along the file, rank, or diagonal they shared.
The motif’s typical setup involves two coordinated long-range pieces — say a rook on a8 and a queen on c8 both eyeing c-file or 8th-rank ideas. A knight or bishop that lands between them, on b8 for example, interferes with their mutual support. The interfering piece may itself be sacrificed; what matters is the separation.
Interference is one of the harder tactical motifs to spot because it requires seeing two enemy pieces as a single unit and recognising that breaking their line is sufficient. A rook protecting a piece on the seventh rank cannot protect it once a knight is sitting between them — even a knight that the rook could capture next move. By the time the rook has captured, the combination has already done its work.
The motif appears most often in endgames where long-range pieces dominate. In the middlegame it tends to be hidden inside longer combinations; the interference move is the second or third move of a sequence, not the first.