What is Back-Rank Weakness?

A back-rank weakness is a vulnerability arising when a player's king is susceptible to a back-rank mate. This typically occurs when the king remains on the back rank without a luft (escape square), hemmed in by its own pawns. A player with a back-rank weakness must constantly guard against enemy rooks or the queen penetrating to the first or eighth rank. Prophylactic measures such as h3/h6 (creating luft) are often necessary to eliminate this weakness.