One advantage of troops that survive fights is that they gain in Veterancy levels, which is much more important than you may initially think. If your in-game units have star icons floating next to them, consider them preferable in many combat situations, as they have attained a rank of Veterancy and the associated bonuses that are awarded with this combat prowess.
Generally, each level of Veterancy is equal to an upgrade of a regular troop type. For example, a three-star Marine unit has about the same combat effectiveness as a raw, just-trained Marine unit with a Medic (#3) upgrade. Although statistically the following varies wildly, the following bonuses are generally awarded to Veteran units:
| Veterancy Level | Additional Damage Inflicted | Additional Damage Resistance |
|---|---|---|
| 1 | +15 percent | +15 percent |
| 2 | +43 percent | +43 percent |
| 3+ | +95 percent | +95 percent |
Units earn Veterancy experience (XP), which isn’t revealed under game conditions and is a complex set of mathematics that may be tweaked continuously. However, the first points of XP are usually awarded when a unit destroys an enemy unit whose costs are equal to around twice their own. Each subsequent point costs twice the amount to earn than the previous point. Note that infantry units have a bonus that allows them to gain Veterancy faster.
The following two examples show how a Scorpion battle tank (worth 25 XP if destroyed by a single unit) and a squad of Marines (worth 5 XP) earn their Veterancy. As each squad varies wildly and the gameplay balance may change, these are for example only:
| Unit | Veterancy Level | XP Needed |
|---|---|---|
| Scorpion | 1 | 40 |
| Scorpion | 2 | 100 |
| Scorpion | 3 | 180 |
| Marines | 1 | 4 |
| Marines | 2 | 12 |
| Marines | 3 | 24 |
Spartans are another unique unit, as they automatically give any vehicle they are in (whether belonging to the UNSC or Covenant) a 15 percent damage and damage resistance bonus, which is augmented by another 15 percent for each upgrade the Spartan receives. So, a fully upgraded Spartan increases the vehicle they are controlling by 60 percent. A Spartan’s Veterancy bonus is also added to the vehicle! This makes them incredibly useful for leading vehicles into battle.