In Grolman/Kazan Chess, if a piece moves from a square where it is protected, the protecting piece follows. In Regimental Ch., from what I remember (I saw a video several years ago), if you move a piece protected by another piece of the same kind, the protector may follow. In both games this applies recursively so pieces can form chains.
So instead of the weakest available piece, it's only pieces of the same type (or maybe pieces that share moves?) that can form these kinds of chains.
In Grolman/Kazan Chess, if a piece moves from a square where it is protected, the protecting piece follows. In Regimental Ch., from what I remember (I saw a video several years ago), if you move a piece protected by another piece of the same kind, the protector may follow. In both games this applies recursively so pieces can form chains.
So instead of the weakest available piece, it's only pieces of the same type (or maybe pieces that share moves?) that can form these kinds of chains.