19. Black blocks its own general, by the soldier

Helpmates in xiangqi

4 moves

Black moves first and both sides cooperate: Black, Red, Black, Red, and Red's second move mates. Black has 45 legal first moves and exactly one of them works. 8 pieces, Black 21.5 to Red 2 in material, mate by the soldier. Themes: Black blocks its own general, a quiet first move…