Interference
Interference is a piece placed directly on the line between a defender and the thing it's defending, cutting the connection without capturing anything and without giving check. It's one of the only tactics on this page where the interposing move can, by itself, do nothing threatening at all and still be completely decisive — its value is purely about what it blocks.
A tactic that wins by doing nothing, on purpose
Almost every tactic described elsewhere on this site works because the opponent has to respond to a threat. Interference is different: the interfering piece can sit there completely passively, not attacking anything, and it still achieves its goal simply by occupying a square. That makes it easy to overlook when you're specifically scanning for checks and captures, since a quiet-looking move that doesn't threaten anything visible rarely gets a second look.
Starting position. A protected knight blocks a queen's own defensive line (illustrative position, not from a recorded game).
The knight blocks the queen's own defensive line without threatening anything itself — and it's protected, so removing it costs material too.
Why the blocker has to be defended
A blocking piece that sits on the exact same line as the defender it's interrupting has an obvious weakness: if the defender simply captures it, the defender is now standing on that square instead, and depending on the geometry, it may still guard everything it did before. The way around this is to make sure the interfering piece is protected, so that capturing it is expensive on its own terms — turning the position into a genuine dilemma rather than a one-move inconvenience the opponent brushes off for free.
Recognizing when interference is available
Look for a single defender responsible for something important along one specific line — a file, rank, or diagonal — and check whether you have a piece that can land on that same line, between the defender and its target, with support from a second piece behind it. If capturing your blocker loses material and ignoring it loses whatever it was protecting, you've found a genuine interference rather than a move the opponent can simply shrug off.
How this differs from a discovered attack
A discovered attack reveals a threat by moving a piece OUT of the way. Interference does the opposite: it puts a piece IN the way. They can look superficially similar because both involve a piece stepping onto or off a line at a critical moment, but one is about unblocking your own attacker, and the other is about blocking the opponent's defender — worth keeping straight, since confusing the two leads to looking for the wrong kind of move in a given position.
What to check before committing to it
The plan collapses if the blocking square can be reached by more than the one piece you're relying on to make it costly — if a second black piece can also recapture, or an entirely different response sidesteps the block altogether (the defender simply abandons the thing it was guarding voluntarily, accepting the loss as the lesser evil), the interference hasn't actually created a dilemma. It's worth calculating both replies to your interposing move in full — capture and non-capture — before playing it, the same way you would for a sacrifice, since a move with no threat of its own gives the opponent complete freedom to choose whichever response actually hurts less.
Interference and clearance sacrifice are mirror images of each other on the same theme — one occupies a square to block the opponent, the other vacates a square to unblock your own side.
Frequently Asked Questions
Does the interfering piece have to be given up eventually?
Not necessarily — sometimes it survives the whole sequence if the opponent chooses not to capture it, since capturing was the worse option to begin with. Whether it ends up lost depends entirely on which of the two bad choices the opponent picks, not on the tactic itself.
Can interference work against two different defending pieces at once?
Yes, in the more advanced version — a single sacrifice placed where two separate defensive lines cross can interrupt both pieces' coordination simultaneously, though positions clean enough to show that clearly are rarer than the single-defender version most players meet first.
Why does interference feel harder to spot than deflection?
Because deflection announces itself with a check or a threat that demands attention, while an interference move can look like it does nothing at all on the surface. Training yourself to ask 'what does this square connect' before dismissing a quiet-looking move is what actually finds these.