What is the fewest number of White chess pieces from the start of a game, that can be placed on a standard chessboard in order to make it impossible to place a Black piece on the board that is not under attack?

Remember,
The final answer must be a subset of the original starting pieces, i.e. only 1 queen, 2 rooks, etc.
Bishops should be on different colour squares.
It is not necessary to attack squares with white pieces on them, as the black piece cannot share a square.

That we don't know for sure yet whether 7 is possible or not.  Somebody out there write a program to solve this!

Posted by David Shin on 2004-09-18 11:12:49