ChessInterference is when an enemy rook, bishop or queen guards a square from a distance, and you drop one of your pieces into the middle of that line to cut the protection. Your opponent either takes the piece you dropped in, or watches the protection disappear. Either way he loses out. It's most common in endgames, so when you play free online chess against the computer and a pawn is close to promoting, it's well worth looking for.
What it looks like
The white pawn is on e7, one step from promoting. But the black rook on c8 guards e8 along the 8th rank, so the moment the pawn promotes it gets taken.
d8 is on the line the black rook uses to guard e8. Once the white rook stands there, nothing Black does works.
Every answer loses
Take the piece in the way
White gives up a rook and gets a brand-new queen. Black doesn't even have his rook left.
Don't take, and the protection is gone
Either way, White gets an extra queen. Notice the pawn on h3: it gives the white king an escape square, so even if the black rook swings around to give check from behind, the king has somewhere to hide.
A real example: a promotion race in the endgame
In rook-and-pawn endgames, the enemy rook often guards the promotion square from the side. That's when you ask: can one of my pieces stand on the square next to the promotion square?
The interference square is diagonally in front of the pawn, so if your opponent takes your rook, the pawn takes back. That's the most useful kind of interference when promoting.
How to defend
- Guard from close up. Guarding from far away along a long line leaves lots of squares in between, and lots of chances to get cut off.
- Bring your king to help. In the endgame the king is a great goalkeeper. When an enemy pawn is close to promoting, the closer your king is, the better.
- Add a second line of defense. If a square is guarded by two pieces from different directions, cutting one line does nothing.
- Ask "what if a piece lands in between?" For every important line of defense, think about whether your opponent has a piece that can drop into it.
Practice puzzles
Show answer
1. Rd8+ The white rook charges to d8, blocking the black rook and giving check too. Black has to take the rook with his rook, and then the pawn takes back on d8 and promotes to a queen. The black king is stuck behind its own pawns. Checkmate.
Show answer
1. Nd7 The white knight jumps to d7, right between the bishop and e8. If the bishop takes the knight, the white rook on d1 takes back, and Black has nothing left guarding e8. If the bishop doesn't take, the pawn just promotes.
Show answer
1. f7 Push the pawn to f7, between the bishop and e8. If the bishop takes on f7, the rook on f1 takes back. If it doesn't, the other pawn promotes next move.
FAQ
Is interference the same as "cutting the line"?
Yes. Interference, line interference, cutting a line: they all mean putting a piece onto your opponent's line of defense.
If the interfering piece gets taken, isn't it just a free gift?
It depends on what happens after the capture. In a good interference, taking your piece costs your opponent something bigger, like letting your pawn promote or getting his king mated. If taking it costs him nothing, it wasn't a good interference.
What's the difference between interference and clearance?
They're opposites. Interference puts a piece into your opponent's line to cut his protection. Clearance moves your own piece out of the way to open your own line.
Try it yourself
Interference is used most in promotion endgames. Go back to chess tactics for the other tactics, or review the most basic one, the fork. The next time you play chess in your browser and a pawn is close to promoting, ask yourself: which line is my opponent using to guard the promotion square?