Frontlines Outbreak Mode: How to Survive the Horde

The most reliable way to win Outbreak is to start somewhere the horde cannot walk to. Zombies never build a port, a transport or a warship, so water stops them completely. On a map where everyone shares one big landmass, the land race is lost by about minute 5.

We read the zombie code and ran headless games on the real engine. Zombies take about 91% of the land in five minutes. In 71 games where the player had a landmass to themselves, nobody was eliminated before the 45-minute clock ended.

There are three ways to win and the clock is the common one

The win checks live in checkWin in the game code. The note next to the clock says that in Outbreak, surviving to the whistle is the win.

Condition	Who wins	How likely
The clock runs out	Any living human (the biggest zombie if no human is left)	The normal ending
Every zombie is dead	The living humans, together	Not seen in our runs
One player holds 70% of the land	That player	A single zombie would need it

The clock is 27,000 ticks, which is 45 minutes at 10 ticks per second. It is multiplied by the world size: 45 minutes on Normal, about 68 on Large (multiplier 1.5) and 90 on Huge (multiplier 2).

Outbreak is also the one mode where humans cannot attack each other. The attack check refuses any attack between two non-zombies in this mode, and every living survivor gets the victory screen when the horde falls. For how to set up a room, read the Frontlines and CONQUEST room setup guide.

The horde is fast, and it goes for you first

A zombie has no economy, no diplomacy and no navy. The comment above its routine in ai.js puts it as "no economy, no diplomacy, no fear". What it has is tempo. We ran 9 zombies through the real Game class for each difficulty setting:

Setting	Seconds between zombie decisions (mean)	Growth and gold multiplier	You, with a capital
Easy	2.7	x1.35	x1.25
Normal	1.9	x1.43	x1.25
Hard	1.2	x1.60	x1.25

Each zombie runs up to 4 attacks at once. If a free tile is next to it, it sends 90% of its available troops there 95% of the time. If a living player is next to it, that player is the target, and the code picks the human first when the human is one of them. At minute 0 a decision hits a living neighbor 75% of the time with 70% of available troops. By minute 30 it is 95% and 95%.

The settings differ less than you would expect. The multiplier and decision rate come from the same table the AI nations use, which we covered in what Easy, Normal and Hard change. Against the horde the difference between Easy and Hard was half a minute of survival.

On a shared mainland the land race is gone by minute 5

We ran 16 games per row on Eurasia, the map of the public Outbreak room, with 9 zombies and one human at a random spawn. We used two deliberately simple scripted players, so treat them as a measuring stick and not as a good player:

• Idle does nothing.
• Builder sets 90% troops, sends everything into free land every second, and builds up to 6 defense posts on tiles that touch the horde. It never attacks a zombie.

Player	Setting	Alive at the clock	Eliminated	Median first invasion (min)	Median elimination (min)
Idle	Easy	2 of 16	14 of 16	4.5	5.8
Idle	Normal	1 of 16	15 of 16	4.3	5.8
Idle	Hard	1 of 16	15 of 16	3.9	5.3
Builder	Easy	0 of 16	16 of 16	2.4	4.9
Builder	Normal	0 of 16	16 of 16	2.4	4.6
Builder	Hard	0 of 16	16 of 16	2.3	4.4

At minute 5 the horde held a median of 90.9% of all land on Easy, 91.7% on Normal and 93.6% on Hard in the idle games that were still running. The builder did worse than the idle player. It reached the zombies sooner, and the first invasion came about two minutes earlier.

If you do fight on the mainland, the combat rules still apply. A defense post multiplies the attack cost on tiles within 8 tiles by 1.6, to a cap of 2.4, and our troops needed to conquer a nation page works through the arithmetic. The horde's attacks are large, though: a zombie throws 70% to 95% of its available troops in each wave.

Water is the one thing the horde cannot cross

The zombie routine, zombieThink, only calls launchAttack on neighbors that share a land border, counting one-tile rivers the way the game does. The code that builds transports and warships sits in the nation and pirate routines. The zombie routine has none of it.

So the question that decides the match is whether a zombie starts on your landmass. We measured it. Each row below is 12 games on the Hard setting (the setting the online room uses) with 9 zombies and an idle human spawned in the middle of the landmass. "Rank" is the landmass's place by size on that map, 0 being the largest. A zombie counts as on your landmass if it owns a tile there at the start.

Map	Rank	Tiles (median)	Share of all land	Zombie there at the start	Alive at the clock when alone	Alive when a zombie shared it
Eurasia	0	58,581	97.7%	12 of 12	no games	3 of 12
Eurasia	1	252	0.4%	0 of 12	12 of 12	no games
Australia & Oceania	0	23,025	91.8%	12 of 12	no games	7 of 12
World	1	4,906	18.3%	2 of 12	10 of 10	0 of 2
World	2	2,696	10.0%	0 of 12	12 of 12	no games
World	3	1,395	5.2%	3 of 12	9 of 9	3 of 3
Thousand Islands	1	3,755	16.2%	7 of 12	5 of 5	4 of 7
Thousand Islands	2	1,512	6.5%	0 of 12	12 of 12	no games
Southeast Asia	1	3,035	14.0%	1 of 12	11 of 11	1 of 1

Add the rows where nobody shared the landmass and the count is 71 of 71 alive at the clock. When a zombie did share it, an idle player lasted in 18 of 37 games. The seven smaller landmasses were shared in 13 of their 84 games, about one in seven. Thousand Islands is the outlier at 7 of 12, and its shape changes with each seed.

Four maps give you nothing to hide on. We counted connected land on seed 1: Pangaea and Twin Continents are each one landmass plus a single stray tile, Strait of Hormuz is one landmass of 71,634 of its 71,710 tiles, and Land of Lakes is 64,090 of 64,475.

Pick your landmass before you click

The spawn phase works in a fixed order. You place your nation first, then the game places the zombies: each one takes the farthest of 40 random land tiles from every spawn so far. You cannot see where they will land.

A sensible plan, with the reasoning attached:

1. Look for a landmass that is not the biggest. A zombie spawn needs a tile. On a map where one landmass is 97.7% of the land, as on Eurasia, every zombie is on it, so the mainland was shared in 12 of 12 games.
2. A tiny island is enough for the clock. The 252-tile Eurasia island held 12 of 12 idle players for 45 minutes. The clock does not ask for land, only for being alive.
3. A zombie on your island is a problem, not a verdict. An idle player lasted in 18 of 37 shared games, so use the ordinary tools: the troops versus workers slider and defense posts on the side the zombie is on.
4. Mind the world size. A bigger world stretches the clock: about 68 minutes on Large and 90 on Huge. That is a longer wait on an island and a longer fight on a coast.

This wins the clock and skips the fight

An island start is a way to win the clock, and it also skips the part of the mode that is a fight. The code names survival as the win, so it is a legitimate result. Whether it is a satisfying one is your call. If you want the fight, the first minutes after your spawn are the ones that count, and what to build first in Frontlines covers that opening.

Most territory games are player against player. OpenFront's own README says players "compete to expand their territory, build structures, and form strategic alliances", and a documentation mirror of the project lists four modes: free-for-all, teams, private lobbies and single player against bots. Co-op against a horde is not among them. We could not confirm that mirror is maintained by the OpenFront team. We make Frontlines and CONQUEST, and OpenFront and territorial.io have far more live players than we do, so this is a point about what Outbreak is, not a verdict.

You can start an Outbreak match from the Frontlines menu with the mode set to Outbreak, or read the FAQ for the short version. Solo, pick the opponent count; every one of them is a zombie.