I'm still not quite sure about the placement of a piece "behind" a pawn. The rules say , "You must place all other pieces on a free space right behind one of your own pawns." Does the new piece have to be lined up vertically totally behind a pawn (orthographically)? Or can the new piece be one row back diagonally "behind" a pawn to the right or left without another pawn being directly in front of it?
For that matter, when you place a new pawn, does it have to be orthographically aligned left or right to a pawn already on the board or can it be placed diagonally left or right of the pawn already on the board--either diagonally one row ahead or diagonally one row behind?
(I probably could have asked these questions using less words.)
Pawns have to be placed directly left or right of other pawns. Other pieces must be placed directly behind a pawn. So all orthogonally and directly adjacent (no other pieces in between).