Editing Retrograde analysis (section)

{{Short description|Genre of chess problem concerned with determining previously played moves}}
{{chess notation}}

In [[chess problems]], '''retrograde analysis''' is a technique employed  to determine which moves were played leading up to a given position.  While this technique is rarely needed for solving ordinary chess problems, there is a whole subgenre of chess problems in which it is an important part; such problems are known as ''retros''.

Retros may ask, for example, for a mate in two, but the main puzzle is in explaining the history of the position. This may be important to determine, for example, if [[castling]] is disallowed or an ''[[en passant]]'' capture is possible. Other problems may ask specific questions relating to the history of the position, such as, "Is the bishop on c1 promoted?".  This is essentially a matter of logical reasoning, with high appeal for puzzle enthusiasts.

Sometimes it is necessary to determine if a particular position is legal, with "legal" meaning that it could be reached by a series of legal moves, no matter how illogical. Another important branch of retrograde analysis problems is [[proof game]] problems.