As old as war itself, Infantry are the foot soldiers of any military force. Underestimated and under-appreciated in the eyes of their so-called betters, many a campaign is often won or lost due to the actions of the "poor bloody infantry" while BattleMech and AeroSpace Fighter pilots win the glory. Their training, equipment, battlefield role and organization can vary wildly, allowing them to fulfill a number of disparate goals. The ability of even the poorest Periphery state or pirate band to field large formations of infantry ensures their use throughout known space, from the Inner Sphere to the Kerensky Cluster.
The advent of Battle Armor has also seen a renewed interest in the use of infantry. Though superior in many ways to their unarmored brethren, their sheer expense and unsuitability for a number of roles sees the continued use of "conventional" infantry.
The cheapest and easiest to maintain, foot infantry are able to cross a wide variety of terrain features, although the lack of any transportation beyond their own legs limits their speed and range of movement. Their most common assignments include static defense, population control, garrison duty and counter-insurgency operations. In addition to their small arms, foot infantry also carry support weapons, though they are limited in how many and what type they may carry.
Motorized Infantry ride into battle on light vehicles such as motorcycles and jeeps, making them faster than foot infantry although more restricted in the types of terrain they can traverse. In addition to the jobs normally given to foot infantry, motorized infantry also act as scouts and forward observers for their parent force. While some will dismount prior to battle, other motorized forces fight from their vehicles, the high speeds and tight formations they typically fight at giving them a reputation for recklessness. Because of their means of transportation, motorized squads are allowed to tow heavier squad support weapons such as Field Guns. They may also be transported to the battlefield in modified heavy APCs.
Mechanized infantry are carried into battle in smaller fighting vehicles (typically weighing less than five tons, compared to the full-sized machines classified under Combat Vehicles) ranging from halftracks to hoverpods and three-man submarines. Offering more protection compared to motorized infantry, these vehicles are also larger and heavier, capable of providing fire support themselves if sufficiently armed. Because of their means of transportation, mechanized infantry using wheeled or tracked vehicles are allowed to tow heavier support weapons such as Field Artillery. In addition to the normal number of infantry, mechanized squads and platoons include enough personnel to man their vehicles.
One of the most expensive types of infantry, jump infantry are trained in the use of Jump Packs, bounding across the battlefield in "hops" of up to 100 meters. This allows them to clear terrain more quickly, and gives them superior mobility to other infantry when operating in an urban environment. One of their primary roles is to hunt down enemy 'Mechs, for which they receive extra training and equipment to accomplish this mission. Jump infantry may also be carried to the battle on transports, favoring in particular VTOL craft. However, without any transportation, jump infantry are limited in the number and types of support weapons they can carry.
While standard infantry formations are useful in most situations, certain environments and missions require specialized infantry, troopers who have received advanced training and equipment to fulfill roles ill-suited to other soldiers. These forces are organized differently, generally smaller in size with fewer soldiers per squad, and include a wide range of roles, from Firefighters and Mountaineers to Combat Engineers and Space marines. For a full list of all infantry types, see Infantry Units.
Gameplay Rules, Notes, and Quirks
Infantry in the CBT BattleTech board game are usually heavily abstracted for the sake of simplicity. Weapon ranges are (generally) toned down to a range where the infantry can only fire their weapons at rather short ranges, even if their rated ranges are much further. The Compound Bow for example is capable of shooting to 160 meters in RPG play, but is abstracted to being a melee weapon in the CBT board game (less than 30 meters, or the same hex), the same category as actual melee weapons, including the Sword, Katana, or the more combat effective Vibroblade, Vibrosword and Vibrokatana (though actual melee weapons have an additional to-hit modifier, since chasing down and stabbing someone within a 30x30 meter area is harder than shooting them with a bow). Laser rifles have an effective RPG range of over 1km, but in CBT play, this is reduced to 60 meters for the short range bracket, 120 for medium ranges and 180 for long. This is done to abstract the actual effectiveness of the unit against an armored target, with the entire unit firing at a it.
The damage formulas can also lead to some unusually high amounts of damage against armor, even though the troopers are unlikely to actually deal major damage when looked at objectively (a bunch of rifles versus what's effectively diamond plated steel in the case of Ferro-Fibrous armor ends up sloughing off a ton of the armor in the case of a "perfect" Auto-Rifle "shot" from a normal IS platoon in CBT play). However, some could argue that since a Machine Gun can damage armor in the BattleTech universe, it stands to reason that infantry should as well. Infantry often can deal more damage than a vehicular machine gun however, especially once their support weapons come into play.
Infantry ammunition usually isn't tracked, with the exception of the Field Gun and Field Artillery classes of infantry, which are assumed to have a ton of ammo, such as would be present as a vehicular ammo bin. This can be any type of ammo as well. 
While a support weapon might need to be reloaded (or recharged) with many individual military power packs, or ammunition belts, often weighing about a tenth of the weapon itself, if not more. This is not considered in CBT play. There is no cap in CBT play for how many times this type weapon can be fired (unless the weapon is specifically one shot), as long as the crew follows the proper movement rules for the weapon (usually meaning they can't move and shoot it in the same turn), and have the crew to fire it, they can fire it.
Due to the way infantry damage works formulaically, an infantry squad in CBT at minimum will deal one point of damage to all targets, assuming they hit, as long as the weapon can deal "penetrating damage" (which basically means it shoots something intended to kill you).This can imply that a squad with nothing more than a Axe as a weapon can deal what can be considered major damage to a (probably light) 'Mech, even if only a single man remains to carry out the attack. This of course precludes Anti-Mech swarm and leg attack tactics.
Non-Lethal weapons (called Non-Penetrating Weapons) can be used, and for CBT play these weapons affect infantry normally in terms of damage, including the fact that the infantry is considered "killed". This is likely due to the fact that needler weapons are categorized in this area as well, instead of their own area. They will not be able to affect armor however. Strangely, even if a platoon is wiped out by non-lethal weaponry, there's still a not insignificant chance that the infantry will end up "dead" when triaged by a medical team. "Normal" weaponry needs a post battle check of 7 or greater per infantryman to have them survive the damage, regardless of the source. In the event of "non-lethal" weapons, the target roll is 5. If that roll fails, the man is considered to be "dead", even though they took the hit by a non-lethal weapon. Proper, fully staffed medical teams and Paramedics can bring that target number down though.
As mentioned above, for simplicity, infantry with their own transport are abstracted into their base motive type, even though it would likely be probable for infantry units to be attached to small Support Vehicles.
The best way to take out infantry is usually with another infantry squad, or Battle Armor, especially if they've dug into hard cover, like a city in which they are defending.
Infantry rolls full fare damage values when attacking other infantry (not counting cover) using the infantry versus infantry tables. Battle Armor with an AP Mount also deals full damage to infantry, and receives damage as though they were 'Mechs with each cluster of damage rolled per suit.
With a few exceptions most vehicular scale weaponry doesn't deal much as much damage to infantry versus a vehicle, and in fact, infantry take significantly reduced damage from most vehicular weaponry. The major exceptions to this rule are the Machine Gun, Small Pulse Laser (and Micro Pulse Laser), the Flamer series and the AP Gauss Rifle (artillery is unwieldy, but counts too). Most other weapons only deal around one tenth the damage they normally would against infantry, and missiles deal half as a result of not being designed to hit multiple targets, granted an infantryman directly hit by an AC/20 round, or even a LRM warhead probably wouldn't be having a good time.
- Total Warfare, p. 23, "Infantry"
- TechManual, p. 145, "Designing Infantry"
- TechManual, p. 275, "Conventional Infantry"
- BattleTroops, pp. 34-35, "Platoon Organization"
- Tactical Operations, p. 311, "Field Guns/Field Artillery"
- A Time Of War Companion p. 168-171 "Converting Personal Equipment to Total Warfare
- Tactical Operations Errata
- A Time Of War Companion p. 168-171 "Converting Personal Equipment to Total Warfare
- A Time Of War Companion p. 171 "Total Warfare Infantry Special Features Table
- Strategic Operations p. 176 "Mostly Dead vs. Truly Dead"
- Total Warfare p. 216 "Non-Infantry Weapon Against Infantry Table"