Interference sacrifice

Definition

An interference sacrifice (often shortened in casual talk to “interference sac”) is a tactical idea where a player deliberately sacrifices a piece by placing it on a critical square to block or cut the line of communication between two enemy pieces. The sacrificed unit literally interferes with the defender’s line (file, rank, or diagonal), forcing the opponent to recapture in a way that leaves a key square or line unprotected, enabling a decisive follow-up—often a checkmate or a winning combination.

In chess problem/composition terminology, interference motifs are grouped into themes such as the Novotny and Plachutta ideas, where a sacrificial move lands on a square that simultaneously disrupts two line-moving defenders.

Usage

How players use the term

Over-the-board and online, players say “nice interference sac!” when a move blocks a rook, bishop, or queen from protecting a vital square. Streamers and commentators also use “interference sacrifice” to describe a clean line-blocking tactic, especially in blitz and bullet. In casual chats you’ll see “interference shot” or just “interference” as shorthand.

Where it appears

Attacks on a castled king, where a rook on the file and a bishop on the diagonal are the main defenders and one sacrificial drop blocks both.
Endgames, where a minor piece is thrown in to block an enemy rook from checking or guarding a promotion square.
Problem themes and studies (Novotny/Plachutta), showcasing pure, elegant interference patterns.

Strategic and historical significance

Why it matters

The interference sacrifice is a cornerstone of tactical play because it converts line control into a concrete advantage: once a defender’s line is blocked, mates, forks, or decisive material wins can appear instantly. It teaches the value of lines, geometry, and coordination—core elements in advanced tactics.

Compositional heritage

Classical problemists explored interference in depth. The Novotny theme places a sacrifice on a square where the opponent’s rook and bishop lines intersect; whichever piece captures interferes with the other. The Plachutta theme is similar, but usually involves two like pieces (often two rooks or two bishops) interfering with each other. These themes influenced practical chess by sharpening players’ awareness of line-blocking motifs.

How to recognize an interference sacrifice

Pattern cues

Two enemy line-pieces (queen, rook, bishop) are coordinating to defend a critical square (often near the king).
There is a square where those defensive lines cross or pass through.
You can plant a piece on that square—sacrificially—to force a recapture that blocks one (or both) lines.

Related motifs

Interference (general line-blocking concept)
Deflection and Decoy (luring defenders off lines)
X-ray and Skewer (line-based pressure that makes interference powerful)
Pin and Zwischenzug (often appear in the calculation around interference sacs)
Plachutta and Novotny (named problem themes of interference)

Examples

Typical attacking setup (verbal diagram)

Imagine Black’s king on g8, a rook on e8 guarding the e-file, and a bishop on g7 guarding the long diagonal to e5/c3. White’s pieces line up with a rook on e1 and a bishop on c4, threatening checks on the e-file and mating ideas on the diagonal. White plays the interference sacrifice 1. Re6!!, dropping a rook onto e6—the intersection of Black’s rook and bishop lines.

If 1...Bxe6, the bishop blocks the g7–c3 diagonal; White may continue Qxg6 or Bxe6+ with an attack now that the diagonal is sealed by Black’s bishop on e6.
If 1...Rxe6, the rook on e6 blocks the e-file for Black’s back-rank coordination; White continues Bxe6+ or Qxg6, crashing through because the e-file/diagonal defenses are mutually interfered with.

The key is that whichever capture Black chooses, one defensive line is fatally interrupted. This is the essence of a Novotny-style interference sac.

Endgame interference (verbal diagram)

White has a passed pawn ready to queen on the eighth rank; Black’s rook both checks from behind and defends the queening square along a file. White throws in a minor piece sacrifice in front of the rook—say, a bishop on the file—to force ...Rxb1 (or a pawn capture), after which the rook’s line is blocked and the pawn promotes with tempo.

Even in time scrambles, players will describe this as “I tossed in an interference sac to shut down his rook.”

Tips, pitfalls, and practical advice

Calculation checklist

Identify which lines defend the target square (rank, file, diagonal).
Find the crossing square and test the sacrifice there first.
Calculate all recaptures: make sure every recapture interferes with at least one vital line.
Verify the payoff: checkmate, decisive material gain, or a winning endgame.

Common pitfalls

Miscounting defenders: if the opponent has a third way to defend, the interference may fail.
Wrong square: placing the piece one square off can become a mere “Speculative sacrifice” without concrete reward.
Time trouble: in Blitz or Bullet, double-check for zwischenzugs or checks you might be allowing.

Interesting facts and anecdotes

From problems to practical play

While the purest interference sacrifices are celebrated in composed problems (especially Novotny and Plachutta themes), they appear surprisingly often in real games as “interference shots” that look intuitive once you see the crossing square. Many tactical puzzles rated “intermediate” to “advanced” in training sets are built around recognizing this cornerstone idea.

Online vernacular

In casual or streamer commentary, you’ll hear phrases like “He just interfered the bishop with a rook sac!” or “That’s a filthy interference sac—blocked both defenders in one move.” It’s a quick, slangy way to celebrate clean line geometry under time pressure.

Interference sacrifice - chess tactic