Anderssen's mate

Anderssen's mate is a coordination pattern on the back rank, the row where the defending side originally placed its king, queen, and rooks. In its most specific form, a rook enters a square next to the king, attacks it, and is protected diagonally by an advanced pawn. It is checkmate when the king is under attack and no legal reply can end that attack.

The roles are exact. The rook gives check and controls squares along the rank. The pawn prevents the king from capturing the rook. That pawn must itself be protected in many versions, because an undefended pawn could be captured to open an escape. The board edge and the king's own pieces complete the net.

The chain behind the rook

8

7

6

5

4

3

2

a1

b

c

d

e

f

g

h

The rook on h8 checks on g8 and controls h7.

The rook enters and the support holds

The rook enters beside the king on a stable support chain. The advanced pawn protects the rook and covers an escape square, while the king supports that pawn and a black piece blocks the remaining exit.

1. The rook on h8 checks on g8 and controls h7.
2. The pawn on g7 protects the rook on h8 and controls f8.
3. The white king on h6 protects the pawn on g7 and prevents the black king from capturing it.
4. The black pawn on f7 occupies an escape square and helps confine its own king.

Variation in naming

Some collections use a broader definition and call it Anderssen's mate when a rook or queen is diagonally supported by a pawn or bishop. Others reserve the name for the rook-and-pawn form described here. The geometry and division of roles matter more than the label because mating-pattern names are not standardized by an official rule.

The practical cue is an advanced pawn controlling the rook's entry square. Before placing or sacrificing the rook beside the king, every capture, block, and escape square must be checked.