Numantian Games left Early Access on 18 June 2019 with The New Empire, a 48 mission campaign carrying more than 60 hours on top of the existing Survival mode. The custom engine pushes up to 20,000 infected on screen at once, and a single one reaching an unwalled house can end a four hour colony in about 90 seconds. Everything hinges on wall placement, noise discipline and the score factor you set before the map generates.
Combat in They Are Billions rewards knowledge over reflexes. Understanding how each mechanic works (and how they interact) is what turns a struggling player into a dominant one. New here? Start with our beginner's guide for the basics.
Core Combat Mechanics
1. One infected can end a run
Infection spreads building to building. A single zombie that reaches an unprotected house converts it, the occupants become infected, and within seconds a chain reaction eats a district that took an hour to build. There is no partial loss in Survival, only a colony that holds or a colony that does not.
Why it matters: This is the foundation of all combat. Everything else builds on this.
2. Noise attracts the horde
Every action has a noise radius. Soldier rifles are loud, Ranger bows are near silent, and buildings such as sawmills and quarries broadcast constantly. Infected Harpies are the most sensitive and can be provoked from 36 tiles away, so a single careless engagement can pull a wandering group into your wall.
Why it matters: The most underrated mechanic. Players who master this early have a massive advantage.
3. Score factor sets difficulty and reward
Before generating a Survival map you set swarm size, map type and duration, and the game converts those into a percentage score factor. Each Survival map unlocks the next by clearing it at a minimum factor, rising from 20 percent for Dark Moorland up to 100 percent for Caustic Lands.
Why it matters: Unlocks a new layer of gameplay depth once understood.
4. Villages of Doom seeded on the map
These clusters hold dense packs of infected including Chubbies and other specials. Provoking one before you have towers means the entire village walks at you at once, so they are cleared deliberately with Snipers or left alone until stone walls are up.
Why it matters: The tactical edge that separates average players from advanced ones.
5. Tesla Tower energy grid
Tesla Towers extend energy coverage across the colony, and defensive buildings need power to fire. If a Tesla Tower is destroyed or infected, every Great Ballista, Shocking Tower and Executor inside its radius goes dark at once, which is how well-walled colonies still collapse.
Why it matters: The endgame optimization mechanic. Small improvements here compound into massive gains.
How These Mechanics Combine
Understanding how mechanics interact is where real optimization happens:
One infected can end a run + Noise attracts the horde
Infection spreads building to building. When combined with Noise attracts the horde, every action has a noise radius. This combination is the core of every effective build.
Score factor sets difficulty and reward + Villages of Doom seeded on the map
Before generating a Survival map you set swarm size, map type and duration, and the game converts those into a percentage score factor. Paired with Villages of Doom seeded on the map, these clusters hold dense packs of infected including chubbies and other specials. This is why the tier list favors builds that leverage both.
Tesla Tower energy grid as a Multiplier
Tesla Towers extend energy coverage across the colony, and defensive buildings need power to fire. If a Tesla Tower is destroyed or infected, every Great Ballista, Shocking Tower and Executor inside its radius goes dark at once, which is how well-walled colonies still collapse. This system amplifies everything else. The better your Tesla Tower energy grid optimization, the more your other mechanics pay off.
Combat by Build
Each build approaches combat differently:
Ranger (A-Tier)
Combat approach: Balanced combat style. Key equipment: Wooden Wall Primary mechanic: One infected can end a run
Ranger offers a solid combat experience. Full setup in our builds guide.
Soldier (A-Tier)
Combat approach: Balanced combat style. Key equipment: Stone Wall Primary mechanic: Noise attracts the horde
Soldier offers a solid combat experience. Full setup in our builds guide.
Sniper (A-Tier)
Combat approach: Balanced combat style. Key equipment: Great Ballista Primary mechanic: Score factor sets difficulty and reward
Sniper offers a solid combat experience. Full setup in our builds guide.
Thanatos (A-Tier)
Combat approach: Balanced combat style. Key equipment: Shocking Tower Primary mechanic: Villages of Doom seeded on the map
Thanatos offers a solid combat experience. Full setup in our builds guide.
Titan (A-Tier)
Combat approach: Balanced combat style. Key equipment: Executor Primary mechanic: Tesla Tower energy grid
Titan offers a solid combat experience. Full setup in our builds guide.
Advanced Combat Techniques
Damage Optimization
- Match your equipment to your build's stat priorities
- Exploit One infected can end a run for maximum damage windows
- Chain Noise attracts the horde and Score factor sets difficulty and reward for combo damage
- Use Villages of Doom seeded on the map to create openings
Survivability
- Learn enemy patterns before committing to attacks
- Use the pause key as a core mechanic, not an emergency button. The game is built around pausing to issue orders, and no amount of mechanical speed will replace stopping the clock during a wave to retarget six units individually.
- Position using One infected can end a run to control spacing
- Save defensive options for guaranteed survival, not comfort
Boss Combat
Bosses test your understanding of every mechanic. See our boss guide for fight-specific strategies.
- Phase awareness: Most bosses change behavior at health thresholds
- Patience over aggression: One extra hit per opening beats dying to greed
- Build preparation: Swap gear and equipment for specific fights when needed
Common Combat Mistakes
- Button mashing: Committed attacks have recovery frames. Mashing locks you into animations.
- Ignoring Noise attracts the horde: This mechanic exists for a reason. Players who use it take significantly less damage.
- Wrong equipment for the situation: Check our weapons guide for situational picks.
- Not learning from deaths: Every death teaches something. If you don't know why you died, you'll die the same way again.
- Overcommitting: Trading hits works in The Deep Forest but will get you killed in Caustic Lands.
More They Are Billions Guides
- They Are Billions They Are Billions Overview
- They Are Billions Best Builds
- They Are Billions Tier List
- They Are Billions Walkthrough
- They Are Billions Beginner's Guide
- They Are Billions Tips & Tricks
- They Are Billions Weapons Guide
- They Are Billions Boss Guide
- They Are Billions Maps & Locations
- They Are Billions Crafting Guide
- They Are Billions Classes & Characters
Similar Games
If you enjoy They Are Billions, check out these related guides:
- Sid Meier's Civilization V Combat Guide: strategy game with similar mechanics
- Mount & Blade II: Bannerlord Combat Guide: strategy game with similar mechanics
- RimWorld Combat Guide: strategy game with similar mechanics
