Warrior Code in the free-to-download game C-evo is one of the first half-dozen advances most nations acquire. You need it before designing any new ground units, and it indirectly allows Theater-building.

C-evo advance, one of the "Early Advances" (not needing Science)

Warrior Code (C-evo): Allows: Barracks and ground units
Has military or other value: Warrior Code allows:
  • ground units, made of your choice of modules (with some restrictions) with each weapons or armor module having a strength of 4 and costing 3 material resources
  • the building of Barracks; a Barracks adds 50% initial strength to all weapons and armor modules of units built in the same city, and it speeds recovery of damaged units there
    Obsoletes: Nothing
Needed for
further advances:

Chivalry, Poetry, and Tactics