Explanation

A long-range piece (rook, bishop, or queen) can protect a piece from afar. However, a long-range defence can be interrupted by moving a piece between the defender and the defended piece. This move is called an interference.

In this level, you can win material with an interference. Interferences are not as common as the other ways to remove the defense. Spotting them can sometimes be tricky, but it will get easier with some practice!

Examples

The easiest interferences to spot are forks:

Black can win with the fork 1...Rg4, attacking the queen on h4, and the bishop on c4 at the same time.
This move is also an interference, because the rook interferes with the queen protecting the bishop.
Note that the queen has no square where she can retreat to and still protect the bishop.

White just grabbed a pawn with Nxb7, but that was too greedy.
Black can now win with the interference 1...e4, attacking the bishop on f3, and also the knight on b7, which is now no longer defended by the bishop.
White is losing a piece.

Sometimes an interference can be used to cut off a piece that has ventured too far into enemy territory:

White controls the only open file with the rook battery, and has a nice advantage.
However Rc7 was a blunder, and now Black can win by cutting off the overextended rook with the interference 1...Bc6!
The rook is no longer protected by the other rook and is trapped.
White has to give the exchange with 2.R7xc6, but after 2...Nxc6 Black has a decisive material advantage.

An interference can sometimes be a sacrifice:

White can win with the sacrifice 1.Be6!, interfering with the defence of the rook, and attacking the queen as well. Black loses at least the exchange, for example 1...Nxe6 2.Qxc8+.

Related motifs

There are various ways to remove the defence. In addition to interference, other ways to remove the defence include capturing the defender, attacking the defender, and deflection.