Back rank

A rank is a horizontal row of eight squares. A side's back rank is the row nearest that player: rank 1 for White and rank 8 for Black. The term is therefore relative to the side being discussed, rather than a fixed rank number.

In the starting position, the back rank holds that side's king, queen, two rooks, two bishops, and two knights. Those pieces may leave later, but the squares remain the side's back rank.

The phrase also appears in “back-rank weakness”: when a king is trapped by its own pieces, an enemy rook or queen may attack along that row and sometimes deliver checkmate, meaning an attack on the king for which no rule-allowed reply exists.