Changes

This endgame with pawn on the 7th rank often occurs after a [[KPKP]] [[Pawn Race|pawn race]] with [[Unstoppable Passer|unstoppable passers]], where the [[Population Count|cardinality]] of their [[Pawn Spans|frontspans]] differs by two with the defending side to move.

A [[Distance|Chebyshev Distancedistance]] of at least four to the [[Promotion Square|promotion square]] with a [[Manhattan-Distance|Manhattan distance]] less than eight for the attacking king is necessary to win that game (<span style="background-color: #c0ffc0;">green area below</span>).While implementing this pattern inside a However, there are positions where the attacking king may reduce the distance due to [[Interior Node RecognizerDiscovered Check|interior node recognizerdiscovered check]], one has to take care that with the king in the corner (i.e. black king on a1), the queen has no mate in one (i.e. on c1).

{|| <fentt border="double" style="font-size:24pt">...Q..../......../......../(....)K.../(.....).../(.....).../(pk...).../([k]k...)...</fentt>| <fentt border="double" style="font-size:24pt">.......Q/......../......../(....)K.../(.....).../(.....).../(pk...).../(kkk....)...</fentt>|-| Draw, &#172;([[King|&#9818;]][[Squares|a1]] &and; [[Queen|&#9813;]][[Square Control|&#10503;]][[Squares|c1]])| Win due to [[Discovered Check|discovered check]]|}

A similar draw motive occurs here with [[stalemateStalemate|stalemate]] after the queen captured the bishop pawn. The <span style="background-color: #c0ffc0;">winning area </span> of the attacking king requires a bit more calculationis depending whether the defending king resides on the [[Pawn Spans|lee-side]] or [[Pawn Spans|luff-side]] . Critical squares for <span id="Lee"></span>==Lee case==The defending king on the [[DistancePawn Spans|lee-side]] is able to threaten [[Stalemate|Chebyshev Distancestalemate]] in the corner. Critical squares are the neighbouring square on the same rank on the [[Pawn Spans|luff-side ]] (i.e. for black pawn on c2, [[Distance|&#977;(&#9812;,d2)]]),and the diagonal neighbouring square on the lee-side one rank back (i.e. for black pawn on c2, b3). Only if the attacking king can reach these squares in one move, it can assist in a [[Checkmate|checkmate]] with the queen - otherwise it is a draw - except the rare cases the attacking king may reduce the [[Distance|&#977;(&#9812;Chebyshev distance]] accordantly,b3)giving [[Discovered Check|discovered check]]). <ref>Lee-case implemented as [[Interior Node Recognizer]] implemented in [[IsiChess]]</ref>* With a <span style="background-color: #c0ffc0;">distance below two</span> to any of these critical squares, the game is won. * A <span style="background-color: #cc80cc;">distance of two</span> to any of these critical squares is required to win the game if the defending king blocks its pawn* Even a distance of two is not sufficient, if the defending king occupies the corner square (i.e. a1), or the 7th/8th (1st/2nd) rank on the neighbouring knight file (i.e. b1, b2).

{|| <fentt border="double" style="font-size:24pt">...Q..../......../......../......../(...)K..../(.+...).../(.kp+.).../[k]k(...)...</fentt>| <fentt border="double" style="font-size:24pt">.......Q/......../......../{....}..../(...){K...}../(.+...){.}../(.kp+.){.}../kk{k.(...)...</fentt>|-| Draw, &#172;([[King|&#9818;]][[Squares|a1]] &and; [[Queen|&#9813;]][[Square Control|&#10503;]][[Squares|c1]])| Win due to [[Discovered Check|discovered check]]|} ==Luff case==When the defending king supports its pawn from the "wrong" [[Pawn Spans|luff-side]], including occupying its [[Promotion Square|promotion square]], the <span style="background-color: #c0ffc0;">winning area</span> for the attacking king is enlarged by at least one move, in luff-direction even two moves.The critical luff-side square is now one file farther away (i.e.for black pawn on c2, e2), and one critical square needs to be reached in two moves now, to either transpose to a winning [[#Lee|lee-side case]], or to assist in a checkmate on the luff-side. {|| <fentt border="double" style="font-size:24pt">......../......../..Q...../(....)..K./(.......)./(.+.....)./(..pk+..)./(..kk...).</fentt>| <fentt border="double" style="font-size:24pt">......../......../.......Q/(....)..K./(.......)./(.+.....)./(..pk+..)./(.......).</fentt>| <fentt border="double" style="font-size:24pt">......../......../.......Q/(....)..K./(.......)./(.+.....)./(..p.+..)./(..k...}.).</fentt>|-| Draw| Win due to [[Discovered Check|discovered check]]| Draw since check parried by [[#Lee|Kb1/b2]]|}

* [https://www.chess.com/article/view/queen-vs-pawn-on-7th Queen vs. Pawn on 7th‎] by TonightOnly, [https://en.wikipedia.org/wiki/Chess.com [Chess.com]], July 12, 2008