Generalized Amazons is PSPACE-Complete

Amazons is a perfect information board game with simple rules and large branching factors. Two players alternately move chess queen-like pieces and block squares on a 10 x 10 playing field. The player who makes the last move wins. Amazons endgames usually decompose into independent subgames. Therefore, the game is a natural testbed for combinatorial game theory. It was known that determining the winner of simple generalized Amazons endgames is NP-equivalent. This paper presents two proofs for the PSPACE-completeness of the generalized version of the full game.