Inspired by this question :
I ask whether the special case ($0$ bishops) will already be sufficient.
More concretely : The game is as follows. Player $A$ places two queens, then player $B$ places a knight on an infinite chess-board. Then, the queens and the knight move alternately. The knight is allowed to capture a queen. If the knight can be checkmated (that is it is attacked and has no way out), then player $A$ wins. If the knight survives forever, player $B$ wins. If the knight is not attacked , but cannot move, we have a stalemate, which is a draw.
I think, the queens can win against best defence. First step is to bring the queens near enough to the knight, second step is to attack the knight from two opposite directions. After trying some constellations, I am convinced that the queens will win assuming best play of both sides.
How can we prove this ?