Scaling your army

There are four basic strategies to improving an army

 * Increase the size of your squads.
 * Have more squads.
 * Improve the lethality of the army.
 * Make the army harder to kill.

And for each basic strategy there are multiple options
And, by the way, they vary by race.

Squad Sizes
Squad sizes increase throughout the game, in response to:
 * Reaching the next tier
 * Purchasing infrastructure - often Tier 1.5, 2.5 or Tier 3.5 structures
 * Acquiring researches
 * Building add-ons

Army Sizes
Each race has two means of increasing the actual army size:


 * Via research: squad cap increase.


 * Via economy boom: second HQ.

Army Lethality & Making the army harder to kill

 * Special weapons, such as Plasmaguns.


 * Squad leaders (and associated researches).


 * Mini-heroes, such as Apothecaries.


 * Standard HP / DPS researches.


 * Squad type specific researches.


 * Commander wargear (via auras).

And everything is a finite resource.
 * Secondary or Tertiary commanders (via abilities).

Strategies form from how you customise your army
Mix and match options in different combinations.

Higher tier units do not make lower tier units obsolete
As the player progresses through the tech tree, they gain access to new units.

In order to ensure the units are balanced, so that the old and new units are not obsolete, certain balancing decisions have been made.

Some require no or few upgrades to be a pressing threat
Most lower tier units have a series of upgrades that make them stronger. Higher tier units often do not.

For instance, Ogryns have high HP and DPS and do not depend on as many upgrades as Guardsmen.

Others possess tactical utility that lower tier units lack
This is usually in the form of mobility.

For instance, Terminators have teleport.

Often they have a different weapon set
Meaning they counter a different set of units.

For instance, Crisis Suits have flamers but other Tau units do not. Thus, Tau get access to another hard counter option.

They are countered by different units
For most races, higher tier units have a different armour type.

For instance, Possessed have daemon armour, which is countered by an entirely different set of weapons than Heavy Infantry armour of the Chaos Space Marine.