Part of the Events Series:

Quick Answer

Infected Horde is an alliance defence event, unlockable every two weeks. It runs about 40 minutes across 20 waves, and an Alliance Leader or R4 has to start it.

The whole alliance township gets surrounded. You defend your own settlement, reinforce alliance-mates who are targeted, and garrison the alliance HQ when it's hit.

The waves that matter:

Wave Target What to do
7, 14, 17 A few random members Reinforce whoever's hit if you aren't
10, 20 The alliance HQ Garrison using the garrison button

The horde stops attacking once your defence fails twice. That's the whole failure condition, and it's why reinforcement discipline decides the score.

Overview

Infected Horde is the friendliest of the big alliance events, in that it's PvE and doesn't hand your losses to another player. It's also the one where casual alliances most consistently underperform, because it demands attention at specific moments rather than continuous effort.

What you'll find is that the event rewards a very small amount of coordination enormously. Twenty people quietly defending their own settlements will score far worse than the same twenty reinforcing each other on waves 7, 14 and 17.

Here's the thing that determines your alliance's result: whether people know that waves 10 and 20 need garrison and the others don't. That's it. That's the skill.

The Wave Structure

Twenty waves across roughly forty minutes. Most waves are ordinary pressure on the alliance as a whole. Five are not.

Waves 7, 14 and 17 — targeted attacks. These hit a few randomly chosen members rather than everyone. If you're one of the targets, you're defending. If you aren't, reinforce someone who is. This is where most alliances leak score, because untargeted members assume they have nothing to do.

Waves 10 and 20 — alliance HQ. These come for the alliance headquarters directly, and they need garrison troops sent via the garrison button. Wave 20 is the finale and the biggest single test.

Everything else is steady defence. Keep your troops home, keep your garrison balanced, and pay attention to chat.

[!IMPORTANT] Two failed defences ends the horde's assault. That sounds like a mercy and it caps your score. Every wave you survive is score you keep, so the goal is depth, not just survival.

What to Do, By Role

If you're a regular member:

  • Keep your troops home and garrisoned for the duration. Don't have marches out gathering.
  • Watch chat for reinforcement calls on waves 7, 14 and 17.
  • Send garrison to the alliance HQ on waves 10 and 20.
  • Keep your garrison balanced rather than specialised.

If you're R4 or R5:

  • Start the event at a time your membership can actually attend. Announce it well ahead.
  • Call the targeted waves in chat as they land. Most members won't be tracking wave numbers.
  • Remind people about garrison on 10 and 20 specifically.
  • Make sure enough members have troops home before you begin.

Preparation

Not much needed, which is part of the appeal. Worth doing:

  • Recall gathering marches before the event starts. Troops out on nodes contribute nothing and are vulnerable.
  • Heal wounded troops so you're at full strength.
  • Check hospital capacity, since wounded beyond it overflow and only part of that overflow is ever recoverable.
  • Have your garrison preset ready so you're not rebuilding a formation mid-wave.

Check the Hospital after repeated waves and reinforcement fights. The healing and Enlistment guide explains casualty categories and how to choose healing batches that suit your alliance's current attendance.

Rewards

Both individual and alliance rewards pay out at the end. Players are ranked individually, and the alliance receives a team score. Individual rewards depend on your ranking and on the score the alliance reached.

That dual structure is why helping others pays you back. Reinforcing a targeted member raises the alliance score, which raises everyone's reward tier including yours.

Plague Zones

Neither of these is the world map's always-available PvE. That is Infected Fiends, which run on Chief Stamina and cap at three Kill Rewards a day.

Worth mentioning alongside, since the two are often confused and share a material.

Plague Zones run weekly, starting Monday and ending Sunday at midnight UTC. You attack or neutralise plague zones to earn epic hero fragments, Chief XP, advanced alloy, and resources.

Advanced alloy matters because it feeds chief gear and badges, and Plague Zones are among the more reliable sources. Infected Horde is another.

F2P vs Spender

F2P accounts should treat this as a priority event. It's PvE, so no troop losses to another player's benefit, and the hero fragments and alloys it feeds are exactly what a free account is short of.

Spending accounts contribute most by soaking the targeted waves and carrying the alliance HQ defence on waves 10 and 20, where raw defensive power matters most.

Common Mistakes

Sitting idle when not targeted. Waves 7, 14 and 17 hit a few members. Everyone else should be reinforcing. Fix: watch chat and send help.

Missing garrison on waves 10 and 20. The alliance HQ needs troops sent explicitly. Fix: know the wave numbers.

Having marches out gathering. Troops on nodes defend nothing. Fix: recall before the start.

Specialised garrison. You don't choose what's coming. Fix: keep it balanced.

Starting at a bad time. R4s scheduling when half the alliance is asleep. Fix: announce ahead and pick a window with coverage.

Ignoring hospital capacity. Wounded troops beyond capacity die. Fix: upgrade it alongside your army.

Related Progression

FAQ

How often is Infected Horde in State of Survival? It unlocks every two weeks and is started by an Alliance Leader or R4.

How long does Infected Horde last? About 40 minutes across 20 waves.

Which waves attack the alliance HQ? Waves 10 and 20. Both need garrison troops sent via the garrison button.

Which waves target individual members? Waves 7, 14 and 17 hit a few random members. Everyone not targeted should reinforce.

When does the horde stop attacking? Once your defence fails twice.

What rewards does Infected Horde give? Individual rewards based on your ranking, plus alliance rewards based on the team score. It also feeds alloys used for chief gear and badges.

What are Plague Zones? A weekly event running Monday to Sunday midnight UTC, awarding epic hero fragments, Chief XP, advanced alloy and resources for attacking or neutralising plague zones.

Key Takeaways

  • Every two weeks, ~40 minutes, 20 waves. Started by an Alliance Leader or R4.
  • Waves 7, 14, 17 target random members — reinforce if you're not one of them.
  • Waves 10 and 20 hit the alliance HQ — send garrison troops explicitly.
  • Two failed defences ends the assault, so depth is the goal.
  • Recall gathering marches and heal troops before it starts.
  • Individual ranking and alliance score both drive your rewards, so helping others pays you.
  • Plague Zones run weekly Monday to Sunday UTC and feed the same alloy economy.