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The Babson task is a kind of chess problem of the form "White to move and mate Black in ''n'' moves against any defence" (a directmate) with the following play: #White makes his first move. #Black defends by promoting a pawn to a queen, rook, bishop or knight. #White responds by also promoting a pawn to queen, rook, bishop or knight respectively. That is, if Black promoted to rook, so does White, if Black promoted to knight, so does White and so on. No other promotion (or any other move) leads to a forced mate in the stipulated number of moves. The task is named after the first person to speculate about the possibility of such a problem, Joseph Ney Babson. It is regarded as one of the greatest challenges for a composer of chess problems to devise a satisfying Babson task problem, and for around half a century the task was considered to be near-impossible in directmate form. Technically, the task can be regarded as a form of Allumwandlung with corresponding promotions by Black and White. An Allumwandlung is a problem which contains, at some point in the solution, promotions to each of the four possible pieces—such problems had already been composed before Babson devised his task. ==Forerunners of the Babson task== This 1912 problem by Wolfgang Pauly is, as it were, a three-quarter Babson task—three of Black's promotions are matched by White. White to move and mate in four: The key is 1.b3, after which there are the following lines: This is not a full Babson, however, because 1...a1=B 2.f8=B does not work – White must instead play 2.f8=Q, with similar play to above. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Babson task」の詳細全文を読む スポンサード リンク
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