According to the rules on Savage Worlds Deluxe (p92), playing characters can affect the outcome of a mass battle by using their Fighting, their Shooting, or their arcane skills.
The heroes of your campaign aren’t likely to sit idly by while war rages around them. Fighters may want to charge the gates, wizards unleash fireballs into the masses, and a gallant knight may ride his trusty warhorse directly into the enemy formations. Those who want to get involved can dramatically affect the results of the battle. Have each character make a Fighting, Shooting, or arcane skill roll (their choice) each action and consult the Character Results below.
The rule is similar to skill challenges in DnD. The character makes a roll. If they succeed, they help their side; they take damage representing wounds from the battle; the more they succeed the more they help and the less damage they receive. The rules are simple and abstract, but allow characters to have an influence in battle and maybe die.
I wonder why Fighting, Shooting, and arcane skills are the only skills allowed. I think there are many other skills that could make a difference in a big battle without any change at all to the rules as they are (i.e. modifiers to skill roll, influence on Battle roll, damage received):
- Boating: the playing character (PC) takes responsibility of moving one of the ships to the space where it is more effective
- Climbing: the PC climbs the mountain by herself, then helps a small faction climb up with ropes, and then they flank the enemy from an unexpected angle
- Driving: the PC steals a truck with additional ammo and brings it crossing enemy lines
- Healing: the PC heals and patches up comrades in the middle of battle, not just in the rear
- Intimidation: the PC's words and gestures lead the main attack against the elite troops of the enemy
- Persuasion: the PC has managed to cross enemy lines and get a new ally or organise a rebellion at the enemies' backyard
- Piloting: the PC's fighter causes many casualties
- Repair: the PC fixes tools, weapons, and machines in the middle of battle, not just in the rear, reducing turnaround time
- Stealth: the PC slides through the enemy's defenses and explodes a bomb
- Swimming: the PC swims to the enemy's mothership and sets it on fire
- Taunt: the PC's words keep morale high making fun of the enemy's faults
Of course, not all skills make sense in all battles. The setting and the GM determine what makes sense and what does not. Driving does not make much sense if you are fighting against Julius Caesar but Fighting does not make much sense either if you are fighting alongside Admiral Ackbar against the Executor and the second Death Star.
I have looked at the official forums but I have not found anything. I also know there is something called the Ultimate Mass Battle Guide but I do not have it, so I do not know if this question is covered there.
Edit (small clarification): I know I can house-rule this, but I am interested in any official source that deviates from SWD and/or the motives behind this design decision.