Explanation

Protecting a square is insufficient, if the protector can be forced away, because it has to capture somewhere else, leaving the square unprotected.

Sometimes a protector has more than one task. It has to protect a piece and a square, or two squares. Such a protector is called "overloaded", if after performing one of the tasks, it is deflected away from doing the other.

The following diagram illustrates the most common ways to remove a defender of checkmate:

White is attacking g7 with the battery on the g-file. Capturing with the queen on g7 would be checkmate if the square weren’t defended by the black knight on e6. But Black's defense is not solid, and White can remove the defender in several ways to win material or force checkmate:

• White can capture the defender with 1.Bxe6. If Black recaptures, White can checkmate on the now-unprotected square g7: 1...Bxe6 2.Qxg7#. Black can avoid checkmate with 1...g6, but then White has won the bishop.
• White can attack the defender with 1.f5. If Black runs away with the knight, g7 is unprotected once again: 1...Nf8 2.Qxg7#. Here Black can also avoid checkmate with 1...g6, but then White captures the knight with 2.fxe6.
• The black knight is also protecting the square d8 against a back-rank mate by the white rook on d1. Guarding two checkmate squares, the knight is overloaded and can be deflected with 1.Rd8+! Nxd8 2.Qxg7#. This is even better than capturing or attacking the defender in this case, because checkmate is forced.
• The knight can also be deflected in the other direction: 1.Qxg7+! Nxg7 2.Rd8#.

Examples

The bishop on h6 guards all the escape squares of the king on g8. The white knight on d5 could deliver checkmate on e7 or f6, but both squares are protected by the queen on d8. The queen also protects the square e8 against mate from the rook on e1, therefore it is overloaded.

White can win with the deflection 1.Re8+!. After the forced reply 1...Qxe8, the queen is no longer defending f6, and White can checkmate with 2.Nxf6#.
Note that starting with 1.Nxf6+? does not work, as after 1...Qxf6 the square e8 is now guarded by the rook on a8.

The rook on e8 is guarding the square f8 against Qf8#, and the square e7 against Ne7#.
It is overloaded, and White can force checkmate with the deflection Qf8+.
After the forced reply Rxf8, the rook is deflected away from protecting e7, and White can deliver checkmate with Ne7#.

How to Spot a Deflection

When you are threatening checkmate, but the checkmate square is protected, always think about ways to remove the defence.
If a protector has more than one task, always check if a deflection is possible.

Related combinations

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