Puzzles: Whose move is it?

All Things Chess
1

For each puzzle below, answer the question “Whose move is it?”. The answer in each case will be either “It must be white’s move” or “It must be black’s move” or “It could be either white’s move or black’s move”.

Puzzle 1:

Puzzle 2:

Puzzle 3:

Puzzle 4:

Puzzle 5:

Puzzle 6:

In all cases, you may assume that the position was arrived at via a sequence of legal moves from the starting position (i.e. from the only legal starting position), and there have been no irregularities, such as incorrect starting position, illegal moves, pieces being displaced and incorrectly replaced, pieces magically materializing out of nowhere, pieces magically disappearing, illegal promotions, etc.

Good luck. See you in 24-72 hours?

Bill Smythe

2

In the first two positions, it’s White’s turn. Both sides have made the same (even) number of moves.

[[Added later: One can’t tell which knight moved to which square, or how. But to get from a position in which White has one knight on a black square and one on a white square, White’s knights must have made an even number of moves. Same for Black.

Also, while the knights are away, the rooks can play, but they are limited to jiggling back and forth one square, so by similar logic, one can deduce that each side’s rooks have made an even number of moves.]]

In the position with a missing knight, Black may have made an odd or an even number of moves, depending on where his knight got captured. So it could be either player’s turn.

In the position with the missing rook, the rook may have been captured on its home square, or it may have been captured on g8, so one doesn’t know whether Black has made an even or an odd number of moves, so it could be either player’s turn.

In the position with the missing bishop where Black has not castled, the rook may have moved an even number of times (e.g. zero) or an odd number (e.g. Rh8-g8, Rg8-f8, Rf8-h8), so it could be either player’s turn.

In the position with the missing bishop where Black has castled, Black has played an odd number of moves. and White an even number, so it’s Black’s turn.

NO WAIT – with the knight off the first rank and the bishop gone, Black could have played O-O, then Kh8, then Re8, then Rg8, then Rf8, then Kg8. That’s an even number of moves for those two crustaceans, so it could be White’s turn.

3

Even knowing the knight was captured on its home square (if it was) wouldn’t tell you. Did the knight starting on g8 and get captured on g8 (even number of moves) and the b8 knight made an even number of moves or did the knight start on b8, get captured b8 (even number of moves) and the g8 knight used an odd number of moves to reach b8.

But if black can still castle king-side (wasn’t specified either way) then it was an even number of moves and white’s move.