"We could kill everyone."
"So what do you think?"
"I'm strangely comfortable with it."
-The Boondock Saints, demonstrating why Soldiers of Fire are a chancy proposition
A Soldier is a human who has been empowered by Heaven or Hell.
The average human has only 5 Forces. Perhaps 10% of the population has the capacity to be invested with a sixth Force and become a Soldier. What exactly determines this capacity is not entirely understood, and individuals who have "tested negative" at one point have later been found to be Potentials. Possibly, some "non-Potentials" could actually become Soldiers, with sufficient exertion from a Superior. De facto, though, only about one human in ten is a good candidate. (And that's just on the level of "can they be empowered" -- not "would they be a reliable Soldier.")
Soldiers can gain additional Forces, and use Essence consciously just as Celestials do. They can also learn to perform Corporeal Songs.
Soldiers of GodEdit
To become a Soldier of God, the human must be made aware of the War, or at least the part of that immediately concerns them. They must understand the great likelihood that they will have to make immense sacrifices, quite possibly ending in their violent death. Only if they have soberly considered this and accepted it is it possible to bind an extra Force and make them into Soldiers.
Soldiers of God are ultimately commanded by Laurence, although in practice they work for their immediate celestial superior. There are approximately 300,000 Soldiers of God on Earth, one for every two angels. This is one area where Heaven is ahead: they have an easier time recruiting Soldiers than Hell. (Salvation's a better perk than damnation, right?)
Soldiers of HellEdit
To recruit a Soldier of Hell, the human must be told about the War, and be fully aware that they are about to sign up with Hell. It is permissible to mislead them somewhat...for example, many Soldiers believe that they will be made into demons upon their death, to continue their work. (In reality, this is not possible...although Forces can be recycled into a new demon, which at least gives the new demon some semblance of the human's self.)
There are about 100,000 Soldiers of Hell on Earth, one for every ten demons.