Answers.Body: <p>Hi and thanks for the question. The words "legal" and "illegal" are actually defined in the FIDE rules. Basically, a legal position is one which can be reached by a sequence of legal moves.</p>
  
  <p>So, with this definition, I think that you are asking: are there illegal positions which aren't obvious? The answer is "many" Welcome to retrograde analysis! :D</p>
  
  <p>There is already a chess.stackexchange question on this, so I suggest we continue the discussion there: <a href="https://chess.stackexchange.com/questions/15210/are-there-any-illegal-positions-that-are-difficult-to-spot">Are there any illegal positions that are difficult to spot?</a></p>
  
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Body: <p>There are some fairly obvious ways to set up a chess board that cannot possibly happen:  both kings simultaneously in check would be one.</p>
  
  <p>There are some positions that <em>seem</em> impossible in a normal game... for example, one side has all of it's original pawns in their original location and the other side has NONE of its pawns remaining - but with both sides displaying all pieces in their original positions (perhaps knights can do this, I don't know.)</p>
  
  <p>However, seems like there may be some impossible positions <em>that are not at all obviously difficult.</em>  </p>
  
  <p>The question is if there are any known legal positions (preferably ones that  a normal human might think are the result of a game) that cannot be played into?</p>
  
Tags: <rules><illegal-move><retrograde-analysis>
Title: Are there any legal positions known to be impossible to come to in a normal game?
ThreadText: # Are there any legal positions known to be impossible to come to in a normal game?
  
  (Asked by: username_0 on 2018-04-03)
  
  There are some fairly obvious ways to set up a chess board that cannot possibly happen: both kings simultaneously in check would be one.
  
  There are some positions that *seem* impossible in a normal game... for example, one side has all of it's original pawns in their original location and the other side has NONE of its pawns remaining - but with both sides displaying all pieces in their original positions (perhaps knights can do this, I don't know.)
  
  However, seems like there may be some impossible positions *that are not at all obviously difficult.*
  
  The question is if there are any known legal positions (preferably ones that a normal human might think are the result of a game) that cannot be played into?
  
  **Tags:** rules, illegal-move, retrograde-analysis
  
  
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  ## 1 answers
  
  ### Answer by username_1 on 2018-04-03. Score: 5
  
  Hi and thanks for the question. The words "legal" and "illegal" are actually defined in the FIDE rules. Basically, a legal position is one which can be reached by a sequence of legal moves.
  
  So, with this definition, I think that you are asking: are there illegal positions which aren't obvious? The answer is "many" Welcome to retrograde analysis! :D
  
  There is already a chess.stackexchange question on this, so I suggest we continue the discussion there: [Are there any illegal positions that are difficult to spot?](https://chess.stackexchange.com/questions/15210/are-there-any-illegal-positions-that-are-difficult-to-spot)
  
  
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