Page "Three-dimensional chess" Paragraph 3

The inventor contended that for chess to be more like modern warfare, attack should be possible not only from a two-dimensional plane but also from above ( air ) and below ( underwater ).

Maack's original formulation was for an 8 × 8 × 8 board, but after experimenting with smaller boards eventually settled on 5 × 5 × 5 as best.

Other obvious differences from chess include two additional pawns per player, and a special piece ( two per player ) named unicorn.