A stack is set of units from allied sides that is formed to create a combat advantage. Each unit in a stack can receive bonuses from other units in the stack, such as, but not limited to leadership, spell and artifact bonuses. As units are added to a stack they add to a stack bonus which maxes out at 8 units, however a stack can be larger then 8. A stack bonus should not be confused with hex bonuses that apply to all units within a hex. The advantage may be for attack or defense, although it is known that you can stack for stealth purposes as well. LIAB Text 50
It could also be that it was simply more efficient for the stacks to be separated, as their move stat was so different that, rather than slow down the fastest units to have them all arrive at the same time.
It is unknown why everyone doesn't just form massive superstacks to maximize bonuses; even if the stack bonus maxes at eight units, it seems that stack-range bonuses, such as the high stack-range component of Leadership, should be spread to as many units as possible (this strategy is touched upon in TBFGK 113). Also, stacks of nine or more units would have a buffer for their stack bonus, delaying the reduction of the bonus as the stack begins to lose units. Possible explanations include:
- Perhaps the limit on maximum stack size prevents it. This reference to a "max stack" appears to suggest this.
- Perhaps the bonuses only apply to the first eight units in the Stack.
- Perhaps each Stack can make a single 'attack', and anything beyond the first eight units isn't counted at all - thus, while it would provide spare durability, you can maximize your damage output by keeping the stacks as small as possible with the maximum bonuses. This would include the assumption would presumably be that you can reconsolidate your stacks quickly as they suffer attrition.
- Perhaps the bonuses actually decrease if a stack exceeds an optimum size.
Assuming Stanley took a max-stack to flee Gobwin Knob here Erf-b1-p077, the size for a max stack appears to be no less than 30 units:
- 3 x Knights +
- 1 x Stanley +
- 1 x Jack +
- 24 x (Group B) dwagons (assuming they all lived, minus the three killed by Ansom) +
- 1 x Stanley's Red dwagon +
- An unknown number of reserve dwagons.