looks like the way to win this is to surround a corner board (top for white, bottom for black) with pawns and have the king in the inner square to block any pieces leaving (the king can't leave its board).
(pawns get promoted to a queen on reaching the furthest side rather than the other side of a board)
This creates an impenetrable fortress that nobody can dismantle?
e.g. for black in bottom left, x=any piece (except knight); p=pawn; k=king:
pppppppp
xxxxxxxp
xxxxxxxp
xxxxxxxp
xxxxxxxp
xxxxxxxp
xxxxxxxp
xxxxxxxK