Troops

Troops are the most important thing to make your power grow because you will need them for killing aliens and players.

To train troops or vehicles you will need to build a Factory or Barracks, at most you can have 3 each

Troops come in 6 tiers, the first tier is automaticly unlocked when you join the game.  To unlock tiers you are required to upgrade your barracks, factory and special buildings 

Here is the tier power of every unit 

Tier 1     -     2  power per unit 

Tier 2     -     8 power per unit

Tier 3     -     20 power per unit

Tier 4     -     36 power per unit 

Tier 5     -     78 power per unit

Tier 6     -     225 power per unit