All the words in red are taken directly from the User's Guide.
Fatigue refers to the detrimental effects combat has on the physical condition of the fighting units. Fatigue values range from 0 (none) to 900 (highest). Within this range, they are further divided into: Low Fatigue (0 to 299), Medium Fatigue (300 to 599), and High Fatigue (600 or higher).
Leaders do not suffer from Fatigue. Fatigue values represent the Combat Fatigue of the unit and are not intended to represent the simple physical fatigue of being winded. When units are fired upon, they may suffer a Fatigue loss as a result. Furthermore, units participating in Melee also suffer Fatigue losses as a result of combat. Units with a Fatigue level of 900 cannot have their Fatigue value increased further, but whenever a Fatigue loss is suffered by such a unit, they must take a Morale Check at the end of the Phase.
If a unit has Medium Fatigue, then
• 1 is subtracted from its Morale value during Morale Checks.
• 10% is subtracted from the melee strength when the unit participates in a Melee attack.
• 10% is subtracted from its fire value when the unit fires.
If a unit has High Fatigue, then
• 2 is subtracted from its Morale value during Morale Checks.
• 20% is subtracted from the melee strength when the unit participates in a Melee attack.
• 20% is subtracted from its fire value when the unit fires.
If a unit has Maximum Fatigue, then
• 40% is subtracted from the melee strength when the unit participates in a melee attack.
• 40% is subtracted from its fire value when the unit fires.
How is Fatigue Calculated?
Fatigue results are calculated as random values between the casualty value and 3 times the casualty value.
Melee fatigue losses are 50% more than normal and, in the case of the melee loser, fatigue losses are double.
A unit may be eligible to recover Fatigue at the beginning of a player’s Movement Phase provided it has not Moved, Fired, participated in Melee, or been Fired upon with any effect from the time of the player’s previous Movement Phase. For each such unit a random value from 0 to twice the applicable recovery rate, determined by Parameter Data associated with the current battle, is subtracted from the unit’s Fatigue value. See the Parameter Data Dialog in the Main Program Help File for the recovery rate values.
Q: Why does it take so long for units to recover from Fatigue?
A:In the game, Fatigue is used to represent combat fatigue, not the physical state of being winded. As such, the physical effects of combat fatigue are felt long term and do not wear off through simple rest. In many Civil War battles, the end of the battle was determined by fatigue and not by losses. In larger battles, commanders had to be careful to rotate their fighting units and not commit any one force too long to battle. Having higher Fatigue recovery rates would permit the unrealistic ability for commanders to rest units for short periods of time and then recommit them to battle, something that was not common historically.
Commentary: It should be clear that the need to rotate units in and out of combat is critical to keep their fatigue levels manageable. Using fatigued troops will lead to weaker Fire Combat and Melee assaults along with a higher probability to both Disrupt and Rout.