When Should You Build Each Structure in OpenFront?

Short answer: do not build from a timer

OpenFront does not have one build order that works on every map. A button becoming affordable is not a reason to click it.

Ask one question first: what problem do I need to solve right now?

Your current problem	Consider building	Wait when
Your Troops keep reaching their maximum	City	Your army is low because you keep attacking or just took heavy losses
Your inland core is safe and already has a City or Port	Factory	The railway has no City or Port to reach
You need control of a sea or have a reliable trade partner	Port	There is no foreign Port in that water and you cannot control the route
An enemy keeps using the same land approach	Defense Post	The front will move immediately or the building will be captured at once
You have a nuclear target and can also afford the weapon	Missile Silo	Building the Silo would leave you unable to buy even an Atom Bomb
An opponent has a believable nuclear threat	SAM Launcher	There is no nuke threat, or the current missile is already about to land

If no structure solves a problem immediately, keeping your Gold is a good decision.

Make three checks before every purchase

Can it work now?

A Factory needs a City or Port where its Trains can earn Gold. Port trade needs another player’s Port in the same connected water. A Missile Silo still needs a separately purchased weapon. A SAM must finish before the attack arrives.

Seeing the structure in the build menu does not mean it is useful in your current position.

Can you keep it?

If the tile under most structures is captured, the whole structure changes owner. A Defense Post is destroyed instead.

That makes the inner part of your country the best home for Cities, Factories, Silos, and SAMs. Ports must sit on the coast, but they still should not be placed on a shore that one quick push can take.

What remains after you buy it?

Do not empty your defense to pay for a long-term plan. Keep enough Troops and Gold to answer the next attack, protect the new route, or pay the next required part of the plan.

City: build when the troop bar keeps filling

Each City level adds 250,000 to your maximum Troops. It does not directly earn Gold, and it does not replace Troops that you already lost.

Good City signals are easy to recognize:

• your army often sits close to its maximum even when you are not fighting;
• you want to hold a larger attack or defense reserve;
• peaceful recovery is about to stop because there is no room left.

If your army is at half of the current maximum or lower, the cap is probably not the problem. You may have just finished a costly war, sent too many Troops, or not allowed enough recovery time.

Upgrade a safe City when you only need more room. The extra capacity applies immediately and does not create another point to defend.

Build a new City when you also need a new Train stop, want to spread your structures, or cannot trust the location of the old City.

The usual City price steps are 125,000, 250,000, 500,000, and then 1,000,000 per level. The later levels are expensive enough that the cap should be a real problem, not a guess.

Factory: build only when a Train has somewhere useful to stop

A Factory sends Trains, but the Factory itself is not a paying stop. Gold is paid when a Train reaches a City or Port.

Use the placement preview before paying. Does the new Factory connect to a safe City or Port? A railway that only links Factories may look busy while earning nothing.

A Factory makes sense when:

• the lobby has not disabled Factories;
• your protected interior already contains a City or Port;
• the railway does not depend on a border that is about to fall;
• your land is safer than the sea.

Factories and Ports share one price ladder. If you already bought one Port level, your first Factory level will usually cost 250,000 instead of 125,000. The same rule works in the other direction.

Upgrade an existing Factory when the network already reaches good stops but needs more Trains.

Build another Factory when a new position connects a different group of Cities or Ports, avoids a risky route, or stops the whole network from depending on one building.

For a closer comparison, read Port vs Factory.

Port: build when the water has a real job

A Port can be valuable in two ways: as a naval base and as the start of sea trade.

If you need Warships in a particular connected sea, a Port may be worth building even without a great trade route. Warships need one of your completed Ports in that water.

If the goal is only income, check all of these first:

• another player’s Port already exists in the same connected water;
• neither side has embargoed the other;
• the route is not extremely short, and the Trade Ships have a fair chance to survive;
• you can protect the Port and the water around it.

Longer trips pay more when a ship arrives. They also expose the ship for longer. A route with impressive theoretical income is worthless if every ship is captured or destroyed.

Upgrade a Port when its water and trade partners are already reliable and you only need more ship traffic.

Build a new Port when it opens another body of water, creates a useful Warship base, changes the available routes, or spreads the risk of losing one coast.

Do not build a Port in an isolated lake just because you expect passive income. Without a foreign destination, its Trade Ships have nowhere to go.

Defense Post: protect a route, not an empty center

A Defense Post strengthens your defended land within 30 tiles.

The first one costs only 50,000 and normally takes about five seconds to build, so it is a strong answer to a real choke point, mountain pass, railway entrance, or approach to your core.

Place it a little behind the front while keeping the expected battle inside its range. The attacker then has to cross strengthened land before reaching the building itself.

Several Defense Posts covering the same tile do not keep multiplying the bonus. A second Post is usually better on another entrance or as a second line if the first position falls.

A Post under construction does not provide the reliable finished defense. Start it before the breach, not after the enemy is already moving through the area.

Later Posts rise to 100,000, 150,000, 200,000, and then 250,000 each. The cheap first Post does not mean every quiet border needs one.

Missile Silo: build when you have a weapon, a target, and spare resources

A Missile Silo costs 1,000,000 and normally takes about ten seconds to build. It does not include a free nuclear weapon.

The smallest complete Atom plan from zero costs:

• Missile Silo: 1,000,000;
• Atom Bomb: 750,000;
• total: 1,750,000.

A Hydrogen Bomb adds a 5,000,000 weapon cost. MIRVs cost much more. A Silo that leaves you unable to buy ammunition is only an expensive target.

Before building, decide what you want to hit, whether enemy SAM coverage makes the shot poor, and whether you can still defend your own core after spending the Gold.

Upgrading a Silo adds another launch slot. It does not shorten the roughly nine-second reload of each used slot.

Upgrade a safe Silo when you need a larger salvo. Build a separate Silo when you need another launch position or do not want one capture or nuclear hit to remove all of your launch capacity.

Use the nuke cost calculator guide for full weapon budgets and ready-slot examples.

SAM Launcher: decide before the missile is in the air

The first SAM costs 1,500,000 and normally needs about 30 seconds to finish. Starting one after a missile warning is often too late.

Begin planning a SAM when:

• an opponent has completed a Missile Silo;
• that opponent appears able to afford a weapon;
• your high-level Cities, economy network, Silo, or main army are concentrated in one valuable area;
• one successful hit would cost much more than the SAM.

A level-1 SAM covers 70 tiles and has one loaded interception slot. An upgrade increases both range and the number of slots. Every used slot still needs about nine seconds to reload.

One SAM is not a perfect shield. A group of nukes or MIRV warheads can fill its available slots.

If your valuable structures are in two distant areas, another SAM usually gives better coverage. If one core already fits inside the current coverage but needs protection from a salvo, an upgrade is more useful.

Read nuclear deterrence and SAM networks for the larger defensive plan.

A simple way to move through a match

Opening

Expand and read your neighbors first. Add a City only when the troop cap is becoming a real limit. Place a Defense Post only on a route that is likely to matter for more than a few seconds.

Do not open by buying one of every structure.

Middle game

Choose one economy that can already work. Pick a Port when the sea is safe and a foreign Port is available. Pick a Factory when protected Cities or Ports can form a useful land network.

Watch a real Trade Ship or Train complete its trip before paying 500,000 or 1,000,000 for later economy levels.

Nuclear stage

Start evaluating a SAM when an enemy Silo appears, not when the incoming warning appears. When preparing your own attack, save the full structure, weapon, and defense budget before placing the Silo.

Six common mistakes

1. “My army is small, so I need a City.” A City raises the maximum; it does not refill the army.
2. “A Factory earns as soon as rails appear.” It needs a City or Port stop that can pay.
3. “A higher Port level makes every ship worth more.” Levels improve traffic, not the payment for the same trip.
4. “More Defense Posts on one spot multiply forever.” Their coverage can overlap, but the combat bonus does not stack.
5. “A Silo upgrade shortens reload time.” It adds a slot; each used slot still takes about nine seconds.
6. “I will build a SAM when the nuke arrives.” The first SAM normally takes about 30 seconds to finish.

The one rule worth remembering

The best structure is not the one you can afford now. It is the one that solves a real problem now and can still work and survive in the next part of the match.

When unsure, return to the three checks: can it work now, can I keep it, and what resources remain after I buy it? Pay only when all three answers are clear.

Use the first-match guide to practice the full flow, or check the structures mechanics page for the current basic numbers.

When the immediate problem is a predictable land route, continue with Defense Posts: placement, timing, and depth. It turns the short Defense Post rule here into a route test, a 50-tick construction decision, and a second-line plan.

Official verification

This guide was checked against the official OpenFront v0.33.9 Release.

Costs, build times, City capacity, and Defense Post range come from the official Config.ts.

Port, Factory, Silo, and SAM behavior was checked against the execution code and tests in the same formal tag.