Soldiers are the primary ground combat unit of the Xenonauts, with vehicles such as the Hunter scout car and the Hyperion hover tank being the secondary combat unit. They are reasonably customisable, as their names can be changed, as well as their nicknames (should they last long enough to get one). They also have an in-depth loadout customisation system, where users can either give them equipment directly, or assign them a pre-made or user-made role, which gives them a set loadout (such as a sniper or a medic etc.).
Depending on armour type, soldiers have varying degrees of durability. A soldier in basic armour will go down in a few Plasma Pistol shots, while a soldier in Predator armour (best armour in the game) will take several turns of fire without flinching, as well as having practically unlimited strength.
As soldiers survive missions and perform certain feats, they will gain points that are randomly spent on points, and will occasioanlly get medals for some actions (such as killing five aliens in one mission). Some points can have a knock-on effect, giving the user more points. One common case of this is increasing the strength of heavy weapons troopers who are too weak to carry a heavy weapon, thus giving them additional time units due to the lack of any weight penalties.
As of Jan. 12, 2016, the manual pdf file that comes with the game gives a much more specific and detailed description of how soldiers' stats level up. According to section 4.9:
"SOLDIER PROGRESSION: Soldiers that survive the battle may receive attribute increases, rank promotions and medals. Skillups are based on performing certain actions, listed below:
- TU: Gained by spending sufficient quantity of TU during the mission.
- HP: Increases incrementally based on the number of other skill-ups gained by the soldier.
- STR: Gained by spending TU on movement when carrying over 80% of carrying capacity.
- ACC: Gained by firing at enemies from within weapon range (you don’t have to hit them).
- RFL: Gained by reaction firing at enemies.
- BRV: Gained after suffering a morale event like panic.
- Rank promotions are based on the total number of skill-ups a soldier has gained.
A soldier can only gain 2 points in each attribute per battle.
Medals are granted for specific actions. They do not provide much in-game effect (They give a small buff to BRV (1-3 depending on medal))) but are a way to remember the achievements of your soldiers!"
Soldiers are expendable, despite being the best in the world. Your men will meet horrible fates one way or another, until you can crank out decent armour (which takes a while). Even Wolf Armour (early-mid game armour) will become worthless against some alien weapons, and some attacks (the infamous reaper is to be mentioned notoriously here).
[article needs images of soldier loadout screens and ground combat scenes of a variety of soldier deaths]