2. For the sake of thoroughness, here are the various ground units in detail. All the Attack and Defend stats increase as your empire's Ground Unit Strength tech increases, but the proportions will all remain the same.
Low Tech Infantry Division - Attack 1.2, Defend 2.5, Cost 60, Size 50
Low Tech Armor Division - Attack 3, Defend 3, Cost 90, Size 50
These two are useful only in that they are your only option in the pre-Transnewtonian era. If you aren't playing in a conventional start you won't need to worry about using them. A low tech unit can be converted into a cadre, preserving the officer corp to reduce the training costs for a more advanced Transnewtonian unit, but I don't play conventional starts so someone else can jump in to talk about that.
Assault Infantry Battalion - Attack 10, Defend 5, Cost 100, Size 5
Mobile Infantry Battalion - Attack 5, Defend 10, Cost 100, Size 5
Heavy Assault Battalion - Attack 12, Defend 12, Cost 180, Size 5
Garrison Battalion - Attack 0, Defend 10, Cost 60, Size 5
These are the basic Transnewtoian ground units. Notice how they are one tenth the size of their conventional predecessors, while their attack and defense values are much higher (except for the Garrison Battalion's attack stat).
Depending on your budget and you expectations of whether you're going to be on offense or defense, you'll want to pick and choose your ground units from these four options, generally. RP-wise, I tend to throw a pair of Garrison Battalions onto each colony as a peacekeeping gendarmerie. It keeps the rabble in line.
Marine Battalion - Attack 10, Defend 10, Cost 180, Size 5
Marine Company - Attack 2, Defend 2, Cost 36, Size 1
Combat Engineers - Attack 10, Defend 10, Cost 180, Size 5
Marine Battalions and Marine Companies double their attack and defense stats when they are in combat aboard a ship, that is when conducting or defending against a boarding action. Combat Engineers double their attack and defense stats when they are in combat defending or assaulting a Planetary Defence Center (PDC).
The Marines have a company sized formation to accomodate the tighter space on board ships, as compared to on A PDC or in the open on a planet's surface. A Small Troop Transport Bay, a Combat Drop Module - Company, or a Combat Drop Module (Cryo) - Company can hold a ground unit no larger than size 1, which is to say only a Marine Company.
When you expect to be conducting operations in the respective areas of expertise of these units, the appropriate unit for the job is better (per unit cost) than the more general purpose Heavy Assault Battalion. On the other hand, when out in the open on a planetary battlefield, a HA Battalion is noticably better than a Marine Battalion, even though both cost the same.
RP-wise, I provide accomodations for Combat Engineers in all my PDCs, and in my largest warships I like to include a security detail Marine Battalion, even if needing to defend against boarding combat is unlikely.
Brigade Headquarters - Attack 0, Defend 2, Cost 150, Size 5
Divisional Headquarters - Attack 0, Defend 3, Cost 250, Size 5
Organizing battalions under a higher formation allows for the base units to gain morale over time, above and beyond their typical maximum of 100, as laid out here:
http://aurora2.pentarch.org/index.php?topic=2308.msg22219#msg22219 Replacement Battalion - Attack 0, Defend 0.5, Cost 40, Size 5
If one of your ground units takes readiness (i.e. hit point) damage, the Replacements sacrifice their readiness to replenish the combatant unit's casualties. If you're going to lose a unit, it might as well be the one that costs one third as much as a HA Battalion, right?
Construction Brigade - Attack 0, Defend 5, Cost 150, Size 25
Forced Labour Unit - Attack 0, Defend 1, Cost 40*, Size 100
These two units function as Construction Factories, without the need to provide the population (and potentially infrastructure) you would normally need to establish a manufacturing sector on given colony. This is useful, for instance, when you want to assemble a prefabricated PDC on an unpopulated world. Additionally, Construction Brigades have an additional use:
recovering installations and technology from alien ruins. Forced Labour Units have additional rules involving their training, as outlined here:
http://aurora2.pentarch.org/index.php?topic=6532.msg69183#msg69183Hope that helps!
