In an orthodox chess composition, there can be three kinds of promoted force in the initial position:
- In the initial problem position there is a piece that can only have come through promotion, so-called obtrusive piece, e.g. a white dark-squared bishop, with pawns b2 and d2 still on their original squares;
- promoted force that adds the number of pieces from the game-array, for instance three rooks or two light-squared bishops of same color (non-standard material);
- pieces the origin of which has been promotion, which can be deducted only by retrograde analysis, i.e. there is nothing in the position that suggests it is promoted force.
The pieces of group (3) are allowed, the pieces of group (1) are tolerated, although avoided, whereas the compositions of group (2) are rejected unless there is, say, a theme tournament for compositions with non-standard material.
See also: Obtrusive piece; Illegal position.