[x] Ability to reinforce siege (via a second attack)
[x] Third parties should only get partial data about a siege
[x] Show number of forces required
[x] After siege is established, order remaining transport groups to land
[x] Siege starts after ground combat finishes.
[x] Show status of siege in News page (show blue indicator)
[x] Show status of siege in tactical

[x] Show news report when a siege starts.
[x] Show status of siege in News tab
[x] Siege status should show up in tactical view


In Era 3 it was common for player empires to attack other players via blitz strategy: massive fleets would conquer world after world, often while the other player was Away From the Keyboard.

We propose a new mechanic that requires the attacker to leave significant numbers of troops on conquered worlds, and gives defending players a chance to counter an invasion. This should restore the balance between attack and defense while increasing the strategic depth of the game.

This proposal must simultaneously meet the following additional requirements:

  • Minimize the set of new concepts introduced to the user.
  • Conquest of independent worlds must remain quick, particularly for new empires.
  • Handle the case where multiple empires are trying to conquer a world, and cases where other empires are trying to help one side or the other.


We introduce the concept of a siege. Under certain circumstances, when an empire invades a world with the intent to conquer, control over the world does not immediately change. Instead, the world enters a state of siege, in which attacking ground troops try to overpower entrenched defenders.

From the perspective of a defending empire, a siege is just like a rebellion, except if the siege wins, the planet joins the attacking empire. As in rebellion, the defending empire can reinforce the planet to decrease the chances of the siege succeeding. Conversely, the attacking empire can also reinforce its forces to increase the chances of success.

Change of control never happens in less than a cycle, giving an AFK player time to respond to an invasion. Even if the defender cannot reinforce the world, they could re-arrange their trade routes to minimize disruption.

However, if the attacking empire does not have enough troops to sustain the siege then the siege ends immediately (and control stays with the original empire). This discourages an attacker from using the same mass of troops to attack from world to world (blitz).

The existence of a siege does not prevent other empires from attacking. If other attacking empires land troops, and if they can overwhelm the sieging ground troops, then the original siege is ended and the new empire starts their own siege.


When a player attacks a world, they are asked to choose the goal of the attack. The following goals are supported:


The goal of an invasion is to become the owner of the world. This goal is valid only if you do not control the world and if you are not currently sieging the world (however, it is valid if someone else is sieging the world).

Combat during an invasion is the same as today (in Era 3). After transports land, troops will fight against defenders. If the attacking troops lose, then the invasion ends, just as today (no siege).

If the attackers win, the defenders retreat and we determine whether a siege is required. If a siege is not required, then the world changes control to the attack as it does today.

[NOTE: For now we require a siege when attacking an imperial world (as opposed to an independent world) but we could add rules about sieges on high-level independent worlds or lack of siege requirements for certain kinds of worlds.]

If a siege starts, we set up defending forces based on the number of retreating troops and other stats for the world (population, tech level, etc.). We might also have additional structure types (e.g., Civil Defense) that increase the power of defenders.

Any remaining defender ships (in fleets or not) retreat to the nearest friendly world, if possible. If they cannot retreat, they fight to the death or surrender.

Reinforce Siege

If an empire is sieging a world, then they have the option to reinforce the siege. This option lands transports on the world and all surviving troops join the attackers.

If there are enemy ships in orbit, they will attack the transports as they land (as a normal invasion). Enemy ships are defined as those belonging to the empire who controls the world, or any (other) empire that is also sieging the world. All other ships are considered neutral.

Reinforce World

If an empire controls a world under siege, then they have the option of reinforcing the defenders of the world. Again, the empire must land transports successfully in order to reinforce the troops. All surviving troops join the defenders.

NOTE: If there are enemy fleets in orbit during a siege, the empire who controls the world cannot simply transfer troops down to the planet. They must go through this path to land transports. In that case, we add a "Reinforce" button instead of an "Attack" button.

Siege Progress

We display the progress of the siege using a similar UI to rebellion. All empires with forces or ships on the world can see the status.

For the defender, we show:

  • Ground forces currently defending.
  • Any modifiers to defense (e.g., from structures).
  • Estimated attacking forces.
  • Any modifiers to attack (if known).
  • Estimated forces required to win the siege (given the current level of attackers).

For the attacker, we show:

  • Attacking forces.
  • Any modifiers to attack.
  • Estimated defender forces.
  • Any modifiers to defense (if known).
  • Estimated forces required to win the siege (given the current level of defenders).

To resolve the siege, we compare attacking forces and defending forces. If attacking forces fall below a certain threshold relative to defenders, then the attackers either retreat or are killed (depending on how overwhelming the defenders are).

If the defending forces fall below a certain level, and if it has been longer than one cycle, then the defenders surrender and the world changes control to the attacker. Some percentage of defenders defect to the winning empire (depending on empire reputation, etc.).

The empire who started a siege can order a retreat and end the siege.

[NOTE: We should change rebellion mechanics to more or less match these.]

Resolving a Siege

The attacker must have sufficient forces to sustain a siege. If the attacker falls below that threshold, the siege ends in about 20 watches.

The defender must have enough forces to resist a siege. If the defender falls below that threshold and the attacker has sufficient forces to sustain a siege, then the world is conquered in about 20 watches or one cycle after the siege started (whichever is greater).

If the attacker has sufficient forces to sustain a siege and the defender has sufficient forces to resist a siege, then the two forces fight each other using normal combat rules. Forces on both sides attrit until one or both fall below the thresholds.

The minimum force for attackers to sustain a siege is equal to one infantry division (or equivalent) per million population of the world.

The minimum force for defenders to resist a siege is equal to one-quarter the strength of the attacking force. For example, if the attackers have 1,000 infantry divisions, then the defenders can resist the siege with 250 infantry divisions.

[Obsolete] Original Proposal

Just as civil wars take a full cycle to give the player a chance to react, maybe invasions of imperial worlds by other empires should take a full cycle, at least for important worlds (capitals, citadels, etc).

This would work like this:

  • Once an empire lands ground troops, an invasion begins. The world does not yet change control.
  • The ground war takes place over a minimum of 1 cycle, with both sides taking casualties as appropriate.
  • The defending player can send fleets to defend the world. Those fleets can attack enemy ships in orbit.
  • The defending player cannot transfer resources or troops to the planet until all enemy ships in orbit are destroyed.
  • Any player can land their own transports with troops to reinforce either defenders or attackers, but they must pass through enemy ships (and possibly ground defenses).
  • All trade routes to the world are suspended and not restored until all enemy ships are destroyed.
  • If the attacking player wins the ground war, the world changes control. [And the other player can potentially blockade the world by attacking.]

It will probably be necessary to end the current goofy system of fleet capture ( if invasions get prolonged.

You present the idea of other players reinforcing the defenders or invaders, but this merits further consideration. What happens to supporting players' troops once the invasion ends? There may need to be more formal war/peace states between empires, or you could end up with weird situations. For example, say Player A could send troops to defending Player B's Betaworld against invasion by Player C. What happens to Player A's troops if Player B then attacks Player A somewhere else? Do Player A's troops continue to fight alongside Player B's troops on Betaworld?

Situations may arise where two or more players want to invade a third empire's planet, but are mutually hostile. How would this be handled? You don't want an ongoing invasion to block other parties from invading a world, or players will call on their allies to initiate minor, non-ship-backed invasions against their own worlds to lock these worlds against the hostile player's invasions.

--imperator-- 23 May 2018:

I support this idea. Long-running invasions will go a long way towards slowing down the pace of the game and slightly offset how much easier it is to attack than defend.

The Problem

The issue with protracted combat is that you could use it to lock up a planet without actually being able to capture it, by just landing a couple troops even if it's not enough to win.

It also makes multi-way combat complicated. A long ground combat phase will result in all kinds of weird permutations of players fighting each other and the game has to be able to handle it.

Having THREE different forms of ground combat- fast combat against independent planets, slow combat against other empires, and virtual civil war combat - is not in the game's interest.

Proposed Solution

I think it makes sense to have ALL ground combat take similar forms with two phases: assault and insurgency. Planets can be associated with two sovereigns, an occupier and a nominal owner. Assault combat is like normal ground combat and quickly determines who occupies a planet. Insurgency combat is like civil war combat and slowly determines who will own a planet.

My proposed solution encompasses civil wars and addresses planetary combat involving multiple empires.

I lay out my proposal in this forum post.

george moromisato 9 Jul 2018:

NOTE: This document has been updated to reflect current implementation in Era 4.