After bombing a base from orbit, you may need to land troops to take control of what's left. Alternatively, you may want to try and take a base intact, in which case infantry and supporting forces are the only option. An invasion force can be made up of six different types of units, each with their own advantages and disadvantages.

Icon	Unit	Cost	MASS	Description
	Riflemen	5	3	Basic infantry platoon, used for holding ground and entering bases. Good against: Engineers. Bad against: APCs, Tanks, Gunships, Artillery
	Engineer	5	3	Specialist infantry platoon equipped with heavy weapons and demolitions. Good against: Tanks, Artillery. Bad against: Riflemen
	APCs	5	4	Used to carry infantry into battle, and also equipped with basic AA defences. Good against: Gunships. Bad against: Tanks
	Tanks	10	2	Armoured fighting vehicles designed to go up against vehicles and emplacements. Good against: APCs, Artillery. Bad against: Gunships
	Gunships	15	2	VTOL or other airborne forces capable of rapid movement and first strike against vehicles, but not so good against infantry which can easily take cover. Good against: APCs, Tanks, Artillery. Bad against: Riflemen, Enginneers
	Artillery	15	2	Heavy mobile artillery, capable of hitting targets at long range. Good against: Riflemen, Engineers, APCs. Bad against: Gunships

All these need to be carried down to the surface. It is assumed that they can all operate in either an atmosphere or vacuum environment, but can't operate in the depths of space.

Each unit consists of 4 elements (a squad in the case of infantry, a vehicle in the case of other units), so each one has 4 'hits' it can take before it is destroyed. Each element can attack, but they all have to attack the same enemy unit.

Any unit has a MASS of 1 when carried in a drop ship. This is because for a short term flight, all the usual support infrastructure isn't required. There must be something capable of carrying the drop ship plus the full MASS to support the units on the board. A unit of APCs can include a unit of either Riflemen or Engineers.

Drop ships need to land near the base to be assaulted in order to offload their troops, though military targets will tend to have AA defences which make landing too close difficult.

The area around a base is divided into hexes which is an abstract representation of the local terrain. Units move into and through hexes and can attack nearby enemy units.

Every light AA unit that a base has can shoot at any drop ship trying to land within 2 hexes of the base. Every heavy AA unit can shoot at any drop ship trying to land within 4 hexes of the base. This makes 5 hexes or further a safe zone where it is generally best to offload troops.

However, any artillery units in the base have a range of 5 hexes, allowing ships to be fired at once they are landed. Most landing may need to be at the six hex range.

Each AA that fires at a target does 1 HIT on a 4-5 (destroying light shuttles), and 2 HITS on a 6 (destroying heavy shuttles). If a shuttle is destroyed, all units within the shuttle are lost.

PDS units can also be used in a light AA role, doing 1 HIT on a 5-6 within a range of 2 Hexes.