All UNSC infantry units benefit from the global infantry upgrades found in the Barracks.
Global Upgrades: UNSC Infantry
| Icon | Name | Description | Tech Level |  Requirements |  Requirements |  Requirements | Time |
|---|---|---|---|---|---|---|---|
 |
Infantry Upgrade I | (All infantry) 10% damage boost. 10% health boost. | 1 | — | — | 400 | 60s |
 |
Infantry Upgrade II | (All infantry) 20% damage boost. 20% health boost. Requires Infantry Upgrade I. | 2 | — | — | 600 | 80s |
 |
Infantry Upgrade III | (All infantry) 30% damage boost. 30% health boost. Requires Infantry Upgrade II. | 3 | — | — | 800 | 100s |
Marines
Unit Class: Core Infantry
Accessed Via: UNSC Bases and Minibases
Strengths/Weaknesses:
- Flexible ground troops
- Quick capture unit
Training Requirements
| Tech Level | Requirements | Requirements | Requirements | Time |
|---|---|---|---|---|
| 0 | 3 | 150 | — | 18s |
Available Research
| Icon | Name | Description | Tech Level | Requirements | Requirements | Requirements | Time |
|---|---|---|---|---|---|---|---|
 |
Grenade Throw | (New ability) Can throw grenades. Small area attack. Cannot target air. | 1 | — | — | 400 | 25s |
 |
Combat Tech | (Unit upgrade) Can repair vehicles, buildings, and air units. Wields rocket launcher. Requires Grenade Throw. | 2 | — | — | 600 | 30s |
Unit Details
Marines are the UNSC’s expeditionary force-in-readiness. After decades in cryosleep, these seasoned fighters are old-school both figuratively and literally. The Spirit of Fire’s Marines are experienced at fighting in exotic environments and have received training by Anders to operate Forerunner systems well enough to avoid triggering defense wards and immolating themselves (most of the time).
UNSC Marine infantry units are armed with assault rifles that are effective against infantry but deal little damage against vehicles. However, these versatile units can be trained to use grenades for impressive burst damage against most ground targets. Marine squads can also be reinforced with Combat Techs—soldiers capable of repairing vehicles, aircraft, and buildings while boosting a squad’s total firepower.
Basic Tactics
A UNSC leader always begins a Multiplayer match with at least two squads of Marines; use them to gather available resources as soon as the match starts.
Marines really shine when it comes to capturing Domination Points and Resource Nodes. A group of three squads is generally enough to clear out any Sentinels that might be guarding a key location. A group of five or more Marine squads should be able to do so with minimal losses.
Marines are fairly inexpensive, and they’re surprisingly versatile—particularly once you’ve researched the Combat Tech unit upgrade. Consider training at least a few extra squads as early as possible, and then upgrade them as you expand your economy. As the match progresses, use your Marines to support more specialized units.
Hellbringers
Unit Class: Anti-Infantry
Accessed Via: Barracks
Strengths/Weaknesses:
- Effective against infantry
- Strong rush unit
- Good against buildings
- Cannot attack air
Training Requirements
| Tech Level | | | | Time |
|---|---|---|---|---|
| 0 | 3 | 80 | 50 | 16s |
Available Research
| Icon | Name | Description | Tech Level | Requirements | Requirements | Requirements | Time |
|---|---|---|---|---|---|---|---|
 |
Dispersion Nozzles | (Weapon upgrade) Sets ground on fire. | 2 | — | — | 600 | 30s |
Unit Details
It takes a special breed of soldier to strap a tank of volatile chemicals to their backs and fire a jet of super-heated flame at enemies. The UNSC may now rely on thermobaric munitions for long-range incendiary attacks, but when it comes to getting up close and personal, the Spirit of Fire’s combat teams still appreciate the value of liquid projector flamethrowers (and the Hellbringers who wield them).
Each Hellbringer carries a heavy flamethrower. These weapons offer a relatively short attack range, but they’re capable of dealing considerable area-of-effect damage. Flamethrowers are highly effective against infantry and structures, but they can’t target air units, and they’re of limited use against armored vehicles.
Basic Tactics
Hellbringers rank among the UNSC’s most effective rushing units. If you plan to overwhelm an enemy during the early stages of a Multiplayer match, consider training a sizable force of Hellbringers as soon as you’re able to construct a Barracks.
Hellbringers can make short work of enemy infantry—even when the target is garrisoned within a structure.
Remember that Hellbringers are vulnerable to vehicles, air units, and other counter-infantry units. Unless you’ve committed to an early rush, avoid sending Hellbringers into battle without appropriate support.
Sniper
Unit Class: Anti-Infantry
Accessed Via: Barracks
Strengths/Weaknesses:
- Very long range
- Detects cloaked units
Training Requirements
| Tech Level | | | | Time |
|---|---|---|---|---|
| 1 | 4 | 75 | 150 | 25s |
Available Research
| Icon | Name | Description | Tech Level | Requirements | Requirements | Requirements | Time |
|---|---|---|---|---|---|---|---|
 |
Active Camo | (New ability) Conceals unit from enemy units without detection abilities. | 2 | — | — | 400 | 30s |
|
Stanchion Sniper System | (Unit upgrade) Increases damage.Requires Active Camo. | 3 | — | — | 700 | 30s |
Unit Details
The Spirit of Fire’s Sniper teams have traditionally operated in the background as the unsung heroes of many skirmishes and aerial strikes. Drawn from experienced Marine force reconnaissance and army cavalry scouts, Snipers are experts at monitoring enemy movements and detecting cloaked units.
The Sniper’s powerful rifle is only effective against infantry, but it’s well-suited to picking off high-priority targets. Each Sniper is also accompanied by a spotter drone, allowing them to identify and monitor enemies from great distances. Snipers can even be equipped with Active Camo, which lets these specialized units cloak themselves for short periods of time.
Basic Tactics
Snipers boast powerful long-range attacks, but they have a low rate of fire and relatively little health. Don’t hesitate to pull back as enemy units close in on a Sniper’s position.
Even with its spotter drone, a Sniper’s range exceeds its line of sight. If you want to minimize the risk of a counterattack, use fast-moving units to identify and distract any targets that might be just outside a Sniper’s field of vision.
Remember that Snipers are only effective against infantry. Focus Sniper attacks on priority targets like Suicide Grunts, Hellbringers, and infantry-based Hero units.
Snipers may lack the speed of dedicated scout units, but they boast an impressive line of sight. Place Snipers on cliffs near enemy bases, or use them to spot targets for deployed Kodiaks.
The Sniper’s Active Camo ability must be researched before it can be used. It’s ineffective against enemies who can detect cloaked units, and it only lasts for about 30 seconds at a time. That being said, Active Camo can greatly increase a Sniper’s survivability and overall effectiveness in the field. If you intend to use Snipers for reconnaissance, consider researching this ability before venturing too deep into enemy territory.
Cyclops
Unit Class: Anti-Vehicle
Accessed Via: Barracks
Strengths/Weaknesses:
- Fast-moving
- Heavy armor
- Cannot attack air
Training Requirements
| Tech Level | | | | Time |
|---|---|---|---|---|
| 2 | 4 | 120 | 150 | 15s |
Available Research
| Icon | Name | Description | Tech Level | Requirements | Requirements | Requirements | Time |
|---|---|---|---|---|---|---|---|
 |
Shock Rounds | (Weapon upgrade) Shots slow vehicles. Increases damage. | 3 | — | — | 700 | 30s |
Unit Details
Though they once served as dedicated melee units, the Cyclops suits produced aboard the Spirit of Fire now feature an autocannon, a refactored exoskeleton, and completely original control software—all of which has served to transform these combat walkers into medium-range tank-killers.
The Cyclops is effective against most ground units, and its autocannon can be upgraded with Shock Rounds that not only increase damage output, but also slow target vehicles. Cyclops suits can’t target air units, but they provide their pilots with enhanced speed and much greater durability.
Basic Tactics
The Cyclops is fairly expensive for an infantry unit, but it can be a big help in fending off encroaching armies. If an opponent is assembling a large group of vehicles, try to supplement your defenses with at least a few Cyclops suits.
A Cyclops moves faster than most infantry units, but it can’t keep pace with light vehicles. Research Shock Rounds to slow enemy vehicles and minimize their chances of a successful retreat.
The Cyclops may have the durability of a light vehicle, but it’s still vulnerable to anti-infantry units—including most of the vehicles it was designed to counter. A small group of Cyclops suits can overwhelm virtually any ground unit, but they tend to take heavy damage during large-scale encounters. If you intend to utilize Cyclops suits, plan to make frequent repairs.
ODSTS
Unit Class: Elite Infantry
Accessed Via: Cutter’s ODST Drop and ODST Assault Group Leader Powers
Strengths/Weaknesses:
- Elite special forces infantry
- Only available to Cutter
- Can be orbital-dropped directly into battle
- Can utilize the Demolition Charge active ability
ODST-Related Leader Powers
| Icon | Name | Description | Tech Level | Requirements | Requirements | Requirements | Time |
|---|---|---|---|---|---|---|---|
 |
ODST Drop | (Tier 3 Leader Power: Cutter) Activate to drop an ODST squad into battle. | — | 12 | 600 | — | — |
 |
ODST Assault Group | (Tier 5 Leader Power: Cutter) Activate to get an orbital drop of veteran units: two Cyclops, two ODST squads, one Scorpion, one Wolverine. | — | 27 | 1650 | 625 | — |
Unit Details
Orbital Drop Shock Troopers (ODSTs) are elite soldiers who can make quick work of most infantry units. A special forces raiding unit of the Marines, ODSTs are deployed from the Spirit of Fire to tip the scales in a close battle, raid enemy bases, capture strategically valuable points, and eliminate high-value targets.
ODSTs are equipped with silenced SMGs and proximity-triggered explosives. They can be deployed anywhere in explored territory using Cutter’s ODST Drop Leader Power, or they can be called in as part of Cutter’s more advanced (and much more costly) ODST Assault Group Leader Power.
Basic Tactics
Cutter’s ODST Drop Leader Power is the first available (and most efficient) way to get ODSTs into battle. If you plan to utilize these elite squads, make sure you spend your Leader Points accordingly.
ODSTs have a shorter attack range than standard Marines, but these elite soldiers are more powerful and far tougher than their core infantry counterparts.
Use the Demolition Charge ability to toss proximity-triggered explosives near enemy structures or in paths frequented by hostile forces.
An ODST squad’s meteoric arrival is one of its greatest strengths—don’t waste it. Their sudden appearance can take an enemy by surprise, and a well-placed ODST Drop can deal significant damage to units caught in the drop zone. Alternatively, you can drop ODSTs directly onto explored Domination Points or Resource Nodes. In these cases, you can capture strategically important points before your opponent has time to react.