I had some difficulties in remembering all the references to the Open Order formation spread all through the rules, so I resumed them and I think it would be useful to other people to have them.
Here they are:
OPEN ORDER (OO)
The following troop types are considered for OO formation:
- Skirmishers, Horse Archers and Tiny units (all restricted to OO formation)
- Light Infantry/Cavalry/Chariots (can adopt OO formation as option)
Other troops can adopt OO only to move in woods (?), rough ground, crossing rivers and obstacles.
DISORDERED OO can use initiative to move away
DISTANCE MODIFIERS (for orders)
- no modifier for Skirmishers, Horse Archers, Light Cavalry in OO
PROXIMITY
- OO can be ignored by other formations.
- OO are affected by proximity rule within 6" (not 12")
MOVING THROUGH (without penalty)
- skirmishers or infantry in OO can move/be moved through
- if both are Light Cavalry/Chariots or Horse Archers in OO
FORMATION CHANGES
- OO can change from or to open order and move as a single move
TERRAIN
- OO have no restriction on rough ground and linear obstacles
- OO have no restriction through woods but cavalry speed = 6" per move
CHOICE OF TARGETS (ranged attacks)
- OO can be ignored (not clear targets)
- OO can direct their attacks in any direction (and divide targets)
CHARGE
OO can charge:
- infantry and cavalry in open order
- artillery, chariots, elephants and baggage
- enemy in buildings
HAND-TO-HAND
- OO close ranks to fight in an engagement, then automatically disperse in OO
EVADE
- only OO can attempt to evade
SUPPORTS
- OO cannot be supported (but can support)
If you find something wrong or missing please correct or add. Thank you.
Aldo

