Fastest Checkmate
What is the smallest number of moves White could
possibly
make in order to checkmate Black?
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9 solutions
The question contains insufficient information
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As it asks for as little moves as possible, you need to take into account every possible move, both if you have already moved the tower or the king, and if you haven't yet. As you can't know, the lowest amount of moves possible is within the possibility that the king and the castle are untouched until then.
The key word is "Possible" - it might be that the king and rook have not moved. (I very much doubt it, but it's possible...)
Yes, this question is missing necessary information. If the king is uncastled then we need that information (otherwise we don't know if it is possible to mate in 1) especially in an endgame puzzle where the chances of this are very low.
It's 2 moves with no castling and 1 move with castling. insufficient info
I wanted to argue the same point myself but the word "possibly", in bold, in the question means, I think, in any possible scenario. I'll admit I didn't see the castling move, because it's unlikely that the board would get to this state without white castling. But, hey, nobody said it would be easy, and castling into a checkmate is pretty badass!
Also, you cannot castle through (or into) check.
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There is no check in the original puzzle; Black doesn't even have any other unit.
In Sam Loyd's puzzle, once you move 1. Qa1, the squares c8, d8, e8 are not attacked, so had the king and rook haven't moved, Black would be able to castle.
If your king and rook have never moved they can castle and give check. The rule is that you can not castle through, into, or out of check. I agree that this is a trick question as a situation like this never moving the rook and kind is impractical l.
If it's asking for the "smallest number of moves possible" then it's reasonable to assume that it could apply in ANY situation. Poorly worded question grammar-wise
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Unless it's been changed in the past 18 hours, the wording is: "What is the smallest number of moves White could possibly make in order to checkmate Black?"
There is no ambiguity here if you understand English grammar and linguistics. When asking "what is the smallest X that Y could POSSIBLY make in order to Z?" the form and syntax clearly imply that the question is searching for the smallest X possible in ANY allowed set of conditions-- not EVERY set. If the latter sense were implied, the construction would need to be "What is the smallest X that Y could make in order to Z in every possible situation?" There's no problem with the wording here.
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I'm sorry but I disagree. When it says "the smallest number of moves possible" it is implied that we don't need to make any further assumptions on our own (e.g. The king and rook haven't moved yet). Given that we can't assume this, we really can't determine the answer to this question. It could be 1, it could be 2. If, however, the question was, "How is it possible for white to checkmate black in one move?", then we would HAVE to construct a specific scenario because it is asking us for conditions. It wouldn't be good for multiple choice though obviously.
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@Jared Lerner – I guess it's how you read it, then, but as a linguist the answer was clear. In your words, the answer could be one, or it could be two. By that reasoning, it's POSSIBLE that the answer is 1, and given that the question asks for the smallest POSSIBLE number of moves, you need to go no further.
To each his own, though :)
In the question you posted black might have moved a peice where currently the white king or queen are. Hence here also it cannot be proved that the king or the rook have been moved
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It is White's turn now. Black cannot have moved something that got captured, because White needs a turn to capture it, making it Black's turn again.
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Oh then it's fine. However it was not mentioned that it is White's turn
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@Aditya Rathi – That's also a convention (just like "castling is permitted unless proven otherwise"). In the same codex, it is stipulated that it's White to move unless it's stated or can be proven otherwise.
Castling being capable at this point is one in a million. I call that a trick question.
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It is. Still, it's a good one :p
One in a million is still possible. Unrealistic, but possible.
When I received the email it said assume the king and rook hadn't moved in the preview box but nowhere in the actual email, or on site. Questions need to be better reviewed before posting.
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A puzzle that gives you specific information like that is basically giving you the solution in the problem setup. The point of this type of question is to test your ability to avoid making assumptions.
How can we be sure that rook and king aren't moved yet... That's not mentioned right??
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Yes, that's exactly my point but the question says possibly and hence we have to assume the possiblity that the king and rook have not moved - thought that probablity is very low
If the answer is possible and it is the smallest number, then it is the right answer. Who cares if they have been moved or not, since there is a scenario where this is possible where they haven't moved, you must assume it to be so and answer correctly!
It doesn't need to be proven that the king and/or rook haven't been moved yet; it just needs to be the case that there's no evidence to the contrary.
In fact, it CANNOT be proven, based only on the information given, whether those pieces have or have not been moved. Without information one way or the other, we're permitted to assume whichever condition we want. Since the question asks for the fewest POSSIBLE moves, and it's POSSIBLE that neither piece has moved yet, the answer is 1.
For that puzzle by Sam Loyd: It is possible that king or rook were not moved and that the last whites move took a piece that moved the last (e.g. white bishop with the queen). The real problem is that you cannot castle through the check.
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It's White's turn. The move right before this was Black's; what was that move?
You can't castle into check/checkmate from either your side or the other. The answer is 2
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Sure you can.. You can't castle into/out of check if you're the one being checked. But Which can castle if he wants to because castling doesn't take white out of, through, or into check. (because there's no black pieces to threaten much of anything.)
The only illegal move for white here is to move his king next to the black king.
I think that it is not necesarily implied that Black has moved the king or rook before. Perhaps the piece of the former movement was captured in Qxa6 or Kxe6.
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In the Lloyd puzzle, it's White to move, which means that Black must have had an intervening move since White's last move. The only pieces which could have moved are the King or Rook.
I suppose it's true that the king or rook must have moved; however, there's another reason here that castling is not allowed: you can't castle through a checked square.
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It's White to move, and White's first move (for the Lloyd puzzle solution) is Qa1, which would have allowed Black to castle, if the King or Rook hadn't moved.
Thanks, this problem made me angry, but you helped calm me.
See, all of you are super smart. Because I just said move the rook to the left diagonal space of the black king.
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"... move the rook to the left diagonal space of the black king." would not put black into check. The king would just take your rook.
Assuming that the rook were guarded, though, you would have moved into a stalemate, not a checkmate.
What a cheesy tricky question. It's virtually impossible to wind up in that end game without ever having moved either the king of the kingside rook. It's unreasonable to make such an assumption, so the fastest checkmate would be in two moves.
I'm the puzzle, what if Black's move on the previous step was a bishop, which was later on taken by the Queen?
the Sam Loyd puzzle, is different because you cannot castle through check, the white queen prevents it. the white king moving under the rook then behind it revealing the 2nd rook, is 2 move mate, and is not dependent on guessing which way round the board is drawn
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The Sam Lloyd puzzle should be drawn with the rook on h8, not a8. The argument still stands: Black cannot castle because his last move must have been either the K or R.
Annoying solution. I think it's not reasonable to suppose you've come into that situation from the beggining of a match without having moved previously, at least, the rook. It could be perfectly stuck to the law, but it is unfair. That's playing with reader's good will. I don't like being cheated by tiny little annoyances like this one.Trick question.
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It's a tricky question, not a trick question. There's nothing in the setup of the problem that makes it seem impossible that the King or Rook haven't moved yet. The whole point of this kind of question is to get you away from assumptions.
1st move : Move king to the right and 2nd move : move king besides the rook checkmate...
Like a lot of other people, I considered the castling but guessed two moves because I found it bizarre that neither king nor rook would have moved this entire game, thus forbidding a castling in virtually all instances of a serious game. But others have correctly pointed out that the question doesn't ask what is likely, it asks what is possible, and in that larger space, there is a puny subset of outcomes where you can castle. I'm not really sure why I dislike this type of question, perhaps because of the ambiguity, or because of how artificial the situation seems - but that could just be a rationalization for getting it wrong.
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I like looking at these as opportunities to remember that strange things can happen in the world. :)
I agree that trick question of this ilk is less than pleasing, as it seems quite unlikely that we'd get to this point and castling still be possible. But that said, it is legal move, assuming neither king nor rook had moved. This is a very similar example, and one that actually happened (which is a plus). http://www.chessgames.com/perl/chessgame?gid=1238144
Quite bluntly, this is a rubbish question.
I agree bad form on the question part. We are to assume that the white rook and white king have yet to move with so many pieces moved already...Bad form indeed
Annoying question. I guess that is why the word possibly is bold in the question, because there is a possible scenario (where castling is valid) that enables a 1 turn win. Feels more like a semantics puzzle than a tactical one though.
In Sam Loyd‘s puzzle Black can‘t castle because otherwise it would go into check, but not because it can be proven that Black moved rook or kind before because White could in the last step beat a figure from Black which was Black‘s last move.
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In Sam Lloyd's puzzle, it's White to move, not Black. If it's White to move, that means that Black must have moved either the King or Rook, because the pawns are unmoved.
it's only happens when white did not move its king.
in your puzzle black cannot castle even if neither rook nor king had moved because he would be ending with the king in check
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You can't castle your king into check. It is permissible to castle resulting in your opponent being in check.
In my puzzle, it is White's turn. After White plays 1. Qa1, White is not attacking c8, d8, e8, so Black can castle if the king and the rook haven't moved.
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So what's stopping it? It is entirely possible that the king and rook haven't moved, because in the previous move white could've taken the black piece that moved last turn. So is there a solution that takes this into factor? Also, Sam Loyd is known for three-move puzzles, so this is weird, being a two-move one.
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@József Inczefi – If it's White's turn, then Black must have moved previously. The unit Black used to make the move couldn't have been captured; White hasn't moved yet to make the capture. The only units Black could have used to make the last move were the pawns, the rook, and the king, because they are the only units present on the board. Among them, the pawns couldn't have made the last move since they are still on their second rank, their starting rank. So Black must have moved their rook or king in the last turn.
That is a pretty big stretch that the King or the Rook haven't moved with so few pieces on the board. You know what assume means.
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The question is about possibility, not likelihood. It's possible that the king and rook haven't moved, therefore possible that castling is the winning move.
Except it is tradition for the king to begin on his color. The white king is on a black space and so it is generally assumed that he has moved.
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Erm... No, it is not tradition for the king to be on his color. Queen always on her color, and the rightmost corner closest to you should be a white square.
Finally, someone noticed
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The king begins on the opposite color, not on his color. The queen takes her color to start.
I forget the name of the move, but u can swap the position of an unmoved king and his unmoved rook. Some people may not know this "advanced" move, or might play under slight variations of the game. Back to the point. This provides 2 horizontal fields of attack, one blocking every space Infront of the king, and one in his own line
u should have mentioned that the king is unmoved
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I agree with you
arth u r right
So true. Bad question.
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The question is about what is possible, not about what is likely. It is possible that a king and rook on their home squares are unmoved, therefore it is possible that castling is the winning move. The whole point of the question is to demonstrate assumption bias.
it said posibble and it is posibble that it is not moved
I did explain that.
the move is called 'castling', and it is only valid if the king is unmoved AND never checked.
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The rule is not "never checked," it's "not in check, and not through check." If your king is checked, but the check is alleviated by another piece, the king can still castle.
I agree @Arth Singh because it is highly unlikely that the King would be unmoved so far into the game. This question with a moved King is (I believe) a 3 move mate.
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Two moves. White king to the right is move one. White king to B row is move two. Mate in two.
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One move. White castles.
The question asks what is the least number possible, not the least number likely.
It's called "castling" in which the king moves two spaces to the right and the rook moves to the space immediately left of the king.
Edit: Yes, castling can result in the king moving in either left or right direction. However, in this particular case, the king would move towards the right side.
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The king can move 2 spaces toward either unmoved rook, and the rook takes position on the other side of the king. Castling is not just to the right.
You cannot Castle when the other player has reached your 'end' of the board....herefore, 2 moves are required to win
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I'm not sure where you got that idea, but the presence of the other king at your end of the board has nothing to do with whether you may castle.
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Also, you dont know if the black king is actually at your side of the board, so if every possibility counts, it is still valid.
The question stated the smallest number of moves possible. As it is possible that the king has not moved i think the answer is valid
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There is no way the you can end up with a board like that and the king or rook hasn't moved
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Are you saying it's highly unlikely, or that it's logistically impossible? 'Cause the first part is true, but irrelevant, and the second part is false.
The question is the shortest number of moves possible. White castles is possible, and mate in one move.
An exposed king in this position - how likely its unmoved or unchecked??
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First, the question of unchecked doesn't matter. The only thing that prevents castling is having previously moved.
Second, the likelihood of its being unmoved doesn't matter, as long as it's possible that it hasn't moved. Because it's possible that it hasn't moved, then it's possible that it can castle, therefore one move is the least number of moves possible.
Should have metioned the white King and Rook were unmoved!!!
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If they'd specifically mentioned that the king and rook were unmoved, that would have immediately led everyone to think of castling. The point of the exercise was to realize that it was possible that they were unmoved, thus it was possible to castle.
its called castling
The move is called castle.
This move is not really 'advanced'. It is a commoner strategy for some players, but not really that level. More intermediate.
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Yes, you are right, its not advanced, its very basic and used by many.
This is late game. Your opponent must either be totally new to chess or you must be one of the top players in the world to NOT move your king in E1 or the rook in H1 even once in the game, which I find highly unlikely...
The only logical explanation to checkmate your opponent has two moves here (If you consider it is late game and your opponent is not new to the game; which will mean that your opponent will give you a challenge and also put you few times in chess as well. The rules to swap your king in E1 with your rook in H1 is that your opponent must NOT put you in chess even once during game play and you must NOT move either your king and rook even once during game play)
That said...The most logical answer to this question will be the following:
Move your rook in F2 to D2. The king in C1 cannot take your rook in D2 since your king in E1 is your backup. (One rule of the game is also, you cannot make move that put your king in chess.) Thus your opponents king in C1 cannot take your rook in D2 and since your rook covers the whole 2th row and the whole column D the king in C1 cannot leave row 1 or move to column D.
The only option for your opponent is to move to B1. After that move, move your king in E1 to E2. That is the final move.
There is one move that you can do, is to swap the king in E1 with the rook in H1. This is the answer they want, which I personally think is an unlogical way of thinking, since it is late game.
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You're applying reasonable expectations to a question that asks what is possible. It is reasonable to assume that the King or Rook have already moved, certainly, so it is unlikely that the Castle would be legal. However unlikely it may be, though, it is not impossible for this position to be reached with an unmoved King and Rook. Therefore, the only correct answer to the question is that it is possible for the King to Castle, resulting in checkmate. One move.
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IMHO it's unreasonable to use an "advanced rule" as a solution to a supposedly logic quiz. 2 moves is the "logical thinking" answer, while 1 move seems more like a teenager trying to look cool in front of his nerd friends (that's totally ok for me) but should not be the actual answer.
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@Rafæl Couto – Castling is a fundamental rule in chess. It's been a standard rule since 1640. Anyone who understands the rules of chess well enough to solve a chess-based logic problem should understand the rules of castling.
I think it would be appropriate for you to delete your comment, since you just insulted the OP, but that's your choice.
If you're offended that a puzzle just taught you or reminded you of a chess rule, perhaps you should reexamine why you're using Brilliant.
castling cannot be done here even if the king and roook are unmoved since the result of this move would leave the king in check.
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Are you talking about the puzzle in the problem, or the puzzle presented in the solution? In the solution puzzle, it's White to move.
You just move white king up one square
I apologise! That is incorrect given it would block the rooks avenue!
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This chess problem is a sleight of hand, and can be considered unethical in the realms of logic. It cannot be assumed that the castle and rook has remained in the same position throughout the game. Such a probability would be considered very low in mathematics. The actual answer is that there are at least 3 outcomes of which one is one move, and the other two of two moves.
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It doesn't have to be assumed that the King and Rook are unmoved, it has to be understood that the possibility exists.
When you state that "there are at least 3 outcomes of which one is one move..." then you've stated that the correct answer to the question, i.e., what is the smallest number of moves white could possibly make, is one.
Doesn't work as the black king would be in check and could move up one square.
Moving the king up would block the white rook guarding the second row, allowing black king to escape to second row.
I agree with Finn C. Just to give a check call its sufficient enough to move the white king one cell up. But That doesnt necesarily give a lock to the black;black king can again escape. But the question was just how to give a check mate.
The answer to the chess question is 2!. The other question is not a chess question is a semantics test.
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The section is "Logic: Level 2"
This is a logic problem, not a chess problem.
you made mistake , at least two moves you have to do, 1- the rook move , up between the two kings
2- the white king goes behind the rook.
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That's two moves. The correct answer is that O-O castling is possible, checkmate.
You cannot move INTO check.
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How would the white King be in check after moving up one square?
The answering being a kingside castle to checkmate is a trick answer that isn't substantiated without a move list (i.e., the correct answer relies on information not available). While technically possible, it's absurd to believe castling would still be permitted in the endgame. Two moves (i.e., rook to D2, king to E2) is the logically correct answer.
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"While technically possible..." means it's the answer to the question, "What is the smallest number of moves White could possibly make in order to checkmate Black?"
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And it's technically possible that an anvil will fall from the sky, killing one of the players, leading to no checkmate at all. This is a question in the LOGIC part of Brilliant, and LOGIC dictates that it's two moves to checkmate even though there is an absurdly tiny corner case where checkmate in one is possible.
Short version: it's a bad question because it relies on an unreasonable assumption.
Why does this have 20 upvotes? This is false.
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Castling... ?
How is it false? Explain.
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King to B2 or King to C2 are both valid moves.
This is late game. Your opponent must either be totally new to chess or you must be one of the top players in the world to NOT move your king in E1 or the rook in H1 even once in the game, which I find highly unlikely...
The only logical explanation to checkmate your opponent has two moves here (If you consider it is late game and your opponent is not new to the game; which will mean that your opponent will give you a challenge and also put you few times in chess as well. The rules to swap your king in E1 with your rook in H1 is that your opponent must NOT put you in chess even once during game play and you must NOT move either your king and rook even once during game play)
That said...The most logical answer to this question will be the following:
Move your rook in F2 to D2. The king in C1 cannot take your rook in D2 since your king in E1 is your backup. (One rule of the game is also, you cannot make move that put your king in chess.) Thus your opponents king in C1 cannot take your rook in D2 and since your rook covers the whole 2th row and the whole column D the king in C1 cannot leave row 1 or move to column D.
The only option for your opponent is to move to B1. After that move, move your king in E1 to E2. That is the final move.
There is one move that you can do, is to swap the king in E1 with the rook in H1. This is the answer they want, which I personally think is an unlogical way of thinking, since it is late game.
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"What is the smallest number of moves White could possibly make in order to checkmate Black?"
When you argue against what is possible with what is likely, you miss the point of the question. It is possible, however unlikely, that the white king and rook are unmoved, therefore it is possible that O-O# is the winning move. (castle kingside)
I agree with Brian. The question is what is possible, not what is likely.
I agree with all of it. 2 is the logical answer. I understand why 1 is the correct answer... Seems to be a bad question anyway because the problem takes place late game and the proposed 1move solution is never available then. People who haven’t played chess will think that this is an option lategame.
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Castling is an option, late in the game, if you haven't moved the king or rook yet. Likelihood and possibility are not the same thing.
Considering this is very late in the game, the likelihood that neither the King nor the Rook in row 1 have ever been moved is very low, thus eliminating possible castling. Moreover, the 'correct' answer implies that white moved only the Rook in row 2 in moves prior to the present positions, again very unlikely. Castling to checkmate is the theoretical answer, but in practical terms the two moves by the white King to unmask the Rook ought to be the answer. I agree with Arvo that it's a bad question. Still, the fact that the word "possibly" is in bold-faced font is a clue that trickery is involved.
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How does a very low likelihood "eliminate" a possible solution? It just makes it a very unlikely solution. The problem is in your approach to the problem, not in the problem setup.
Except that "possible" and "likely" are two different things. It would be very strange to happen this way in practice, but it could happen this way.
It never says otherwise.
I agree to Finn c
Castling assumes that the Rook and King have never been moved ... just because they are now in their original positions does not mean they have never been moved ... for this to be the correct answer the question should have stated that they have never been moved else at this point of a game one must assume this not to be the case!!
Dyane is right , you can't be sure to checkmate in 1 move.. Because you suppose the king never move... For me the right answer is 2 move !!
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I agree. We are to assume facts not in evidence.
i would say that this question is more sutible for those who wanna become good chess player but its a good way to learn about castling
- O-O
In such a position many people will forget that castling might be still possible, in addition to the people who are a little hazy on the move itself (or not so hazy like a famous coffee house hustler who would castle queen side to the c and b files and when called on it, according to legend, said "You castle your way, and I'll castle mine").. That's the main trick. The other, the only possible flaw, would be if some retrograde analysis were to show that the white king or rook must have moved before reaching this position. I am sure enough that I could concoct some far fetched set of moves to dispose of all the missing wood without moving the white king and rook in what amounts to a very long messy helpmate, so that's my answer.
It is a loaded question, because the observer is not given enough information. Yes,the check mate maybe done in one move by castling providing that the white king has not moved. BUT! If the white king has moved before, then it takes three moves to check mate.
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Only two moves. 1. Rd2 Kb1 2. Ke2#
That’s why it say « could possibly »
in this case we can use the elephant and directly do check mate
Take one board of a single value of blocks, the blocks are considered possibilities. You then times each move by its corrosponding possibilities on the board, then you figure out the variables that may change the value of the game, such as the ability to move 3 instead of one blocks, or the ability to swap a piece, from there you look at your opponents possibilities, and then reduce each possibility with that of your own and come out with an outcome of 0 for your opponent, . You then multiply the value of the possible moves by that of he corrosponding moves (p moves), which is really just a repeat of the first step.... Or you could just look at it and think over it for a bit, and then realize it's only one move that is needed.
These types of problems posed in this fashion area designed to mislead you so, in my opinion, they are not very satisfying because they are somewhat "false". In this example we were not told whose move it was and that white had yet to castle.
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It wouldn't matter whose move it was, because the question asks for the number of moves white would take to win.
The question asks what the "fewest possible" moves would be, and from the position it is possible that White had not yet castled.
There is no misinformation or lack of information in the problem setup. In fact, if they had specifically mentioned that the white king hadn't moved yet, everyone would have immediately castled.
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Fewest number of moves "possible" should mean always possible, not sometimes possible. While there's no misinformation here, it's just not worded very well in the context of a riddle.
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@Jared Lerner – It's always possible, without further information, that a piece in its home position has never moved.
For the record, I answered "2".
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@Brian Egedy – Actually a piece in its home position does not necessarily mean it has not moved since a piece can always simply be moved back to it original position on the next available turn unless there is a check on the board. However, I'm splitting hairs. For the record I choose "2" as well, but I don't feel too bad since this question is like asking what is possibly the shortest distance between to points (a,b). Almost everyone responds with the distance of line segment ab, but then the author responds, "No," the answer is zero since you could "possibly" teleport. The author allows this question so much ambiguity to add to its difficulty, but in the end the answer is something that cannot be implied by the given circumstances since as I have previously stated anyone of the pieces on the board may have been moved. One can guess the answer and be correct, but no one can know they are correct because this information is not a "given". Just because a pieces appears to have never moved does not mean it has not. Also, I apologize for the use of teleport since it clearly trivializes my counter example, but hey it's the internet and I couldn't resist since castling is one of the few moves in chess which allows pieces to "teleport" across the board and not simply "move". Also as an aside, chess books purposely pose questions similar to this with an exact number because it removes any sense of trickery and only leaves the player to act cleverly and logically not hypothetically. I suggest we also strive for puzzles that mirror these qualities.
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@Brian Zohorsky – Not to split hairs into atoms, but I said it's possible that a piece in its home position has never moved, not that it's impossible for a piece to return to its home position.
This is a chess riddle, not a chess puzzle. There is no expectation against "trickery" here.
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@Brian Egedy – I think it all depends on how people are interpreting the question. My take on it is:
"What is the smallest number of moves possible?"
1: if the king and rook haven't moved 2: if either one of them have
And since there are two possible scenarios, I don't think we can arrive at a definitive answer.
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@Jared Lerner – "Is it possible that the King and Rook haven't moved?" Yes Then the smallest number of moves possible is 1.
The point of this type of puzzle is to remind you not to make assumptions. The assumption that most people make here is that the position and game have progressed too far for it to be reasonable to think that Castling is still an option, so they discount it, if it even occurs to them. This discussion is the purpose of this type of question.
For me, your last sentence is spot on. Anyway, it's immaterial, I still find this type of question unsatisfying as it is too artificial.
I'm with you Brian, it's a beautiful puzzle. Congratulations, Alexander. You had me bluffed!
It is very unlikely that at that stage of the game with so few pieces, the king and his tower had not made any move. Ability to castle is not to be realistically considered.
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It's not a chess question, it's a logic question in a chess framework. The question is what's possible, not what's likely, realistic, or reasonable.
It's possible that a fair coin could land heads-up 1,000 times in a row. It's not realistic, or reasonable, but there is still a probability that describes the fact that it's possible.
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You can only answer a question or solve a problem with the data given ... there is nothing that says the king is even on the right side of the board ... these are bad trick questions designed to be clever, not comprehensive.
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@Bp Kline – Again, it is possible that the king is in its starting position, it is possible that the rook is in its starting position, and it is possible that neither have moved, therefore it is possible that castling is a legal move. This is a logic puzzle, not a calculation.
1 move???? NO.
Since you do not know the history of the game, you cannot castle. Maybe the king is on the whole other side of the board - who knows. You cannot assume that.
I am really getting to dislike and ready to unsubscribe from this site because of badly thought out questions.
My take on this is that if you move the while king, the only significant place you can move him exposed the rook on his same row, meaning you have to block the other rook and the black king can then move out of check from the first rook.
I think you have to move the rook on the second row to the northwest square of the king ... sorry, i am not an expert at chess, and then move the white king forward.
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Since the question doesn't even say that it refers to the position of the pieces in the attached diagram it could refer to any board you care to draw. In which case the answer can always be as low as one.
And that explanation is just as fatuous as the stupid castling solution that's been given.
A bit like what does 10+10 equal.. oh 100 (because in the question setter's head he was in binary mode)
Muppetry
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It's a logical riddle in a chess framework. Compare it to puzzles that require lateral thinking to find the solution. Given this board, and these piece positions, isn't it possible that the King and Rook are unmoved?
The question isn't what move you would play, the question is what is the least possible number of moves to achieve checkmate. It's a logic puzzle, not a chess problem.
The most efficient two-move solution is Kf1 (King one square to the right) and after the black king moves either left or right, the white King moves to g2 (northeast from f1), exposing the black King to the bottom-right Rook.
The question is what is possible, not what is likely.
Without Castling! The top Rook moves 2 places left, black moves 1 place left, the White King moves 1 place forward behind the Rook that moved.
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That's a solution for "white to move and win", but it doesn't solve the logic puzzle of "what is the lowest possible number of moves"
Move the rook on top two spaces left
That's BS. We're supposed to assume the king has not moved or castled yet, but the only pieces on the board are two rooks and two kings?? So misleading.
At first, it sure looks like a mate in 2: 1. Kf1 any 2. Kg2#. Can it be faster?
By Codex of Chess Compositions , a side is permitted to castle unless it can be proven that the king or the rook has moved before. Here, it cannot be proven so (it's easy to construct a game where the king and the rook haven't moved before), so White is allowed to castle, and 1. 0-0#! mates in one. Thus the answer is one move .
Compare this to this puzzle by Sam Loyd:
Here, it can be shown that Black has moved the king or the rook before (otherwise, what was Black's move before this?), thus Black cannot castle, allowing the intended solution 1. Qa1 any 2. Qh8#.