be a previously captured piece. Promotion is mandatory when moving to the last rank; the pawn cannot remain as a pawn.

Promotion to a queen is known as queening; promotion to any other piece is known as underpromotion. Promotion is almost always to a queen, as it is the most powerful piece. Underpromotion might be done for various reasons, such as to avoid stalemate or for tactical reasons related to the knight's unique movement pattern. Promotion or the threat of it often decides the result in an endgame.