Undermining

Undermining attacks the support of a position instead of striking the visible target first. If a piece or pawn is safe because another unit protects it, the attacker captures, exchanges, or threatens that defender. Once the support disappears, the target becomes undefended or inadequately defended.

Attack on the Tactical Support of a Piece or Square

A Pinned Defender Can No Longer Serve

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a1

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Start

Bd4

a5

Qh7#

The defense from f6 makes Qh7+ fail to Nxh7.

The support still works

The black knight on f6 protects h7 and can answer an immediate queen entry.

1. The defense from f6 makes Qh7+ fail to Nxh7.

The idea is common in pawn chains, diagonal groups of pawns that protect one another. Attacking the base may weaken several pawns at once. A pawn lever, a pawn advance that creates contact with an enemy pawn, can produce the capture needed to destroy that base and open lines for the pieces.

Attack on the Practical Base of a Pawn Chain

c6 Holds the Pawn Chain Together

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a1

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Start

bxc6

e3

Nxd5

Nxd5 still fails because the pawn on c6 can recapture on d5.

Chain and target

The pawn on c6 supports d5, and d5 supports e4. Playing Nxd5 first allows c6 to recapture.

1. Nxd5 still fails because the pawn on c6 can recapture on d5.

In many sources, undermining and removal of the defender are synonyms. Here, undermining emphasizes the support relationship, especially in pawn structures, while removal of the defender names the direct capture of the protecting piece. The concrete position matters more than the label.