Queen versus bishop and knight ending

In this pawnless ending, one side has a king and queen, while the other has a king, bishop, and knight. The queen normally wins, but the result is not determined by piece count alone. The exact position and the defender's ability to keep all three pieces connected are critical.

The queen side tries to check from changing directions, restrict the opposing king, and create double attacks, meaning threats against the bishop and knight at the same time. The attacking king must approach to remove escape squares and help capture a piece. Checks without a plan to bring the king closer may allow the defense to preserve its formation.

The defender wants the king to protect the bishop and knight, with the minor pieces also protecting one another. If either piece becomes distant or undefended, the queen can attack it while continuing to check the king. The main defensive goal is Karstedt's fortress, a precise arrangement in which king, bishop, and knight form a barrier that blocks the enemy king's approach.

The fortress does not mean that every compact setup draws. The queen can usually prevent its construction while there is still time to separate the pieces. Tablebases, databases that exhaustively calculate endings with few pieces, confirm both the queen's normal win and the exceptional drawn positions.