FleetCoordinationSystem (FCS)

Overview

Fleet Coordination System (FCS) lets an attack leader open an outgoing attack to alliance members. Allies can attach their own fleets to the same target before the group arrives. When every fleet in the group has reached the target, they fight one combined battle against the defender.

In the fleet UI this appears as:

Solo attack — standard attack, no allies can join
Open to alliance — coordinated attack rally

FCS is only available for attack missions and can be participated only by alliance member or members of an ally alliance

Starting a Coordinated Attack

When launching an attack, the leader can:

Toggle Open to alliance to make the fleet participatable.
Set Max delay if allies join late (see ETA & Delay Logic).

If no allies join before arrival, the attack resolves as a normal solo attack — FCS grouping only affects combat when at least one ally participates.

Defender notification

The target is notified when the leader launches, using the leader’s original ETA. Ally fleets joining later do not send additional incoming-attack notifications.

Alliance members receive a rally notification when a coordinated attack is created.

Joining a Rally (Participation)

Alliance members can join an open rally from the fleet list (FCS filter) while the lead fleet is still traveling.

Requirements to participate

Requirement	Details
FCS enabled	Feature must be active for the joining player
Same alliance	Active membership in the leader’s alliance
Same realm	Same realm level as the attack leader
Attack still open	Lead fleet must be `traveling`, mission type `attack`, participation not locked
Not the leader	You cannot join your own rally
One fleet per player	Only one fleet per player per rally
Rally not full	Default max: 2 allies (server config: `fcs.maxParticipantSlots`)
ETA rules	Your fleet must be able to join without breaking the leader’s max-delay setting

What happens when you join

Your fleet participates in the initiator attack fleet
Alliance members are notified that someone joined.

Locking Participation

Only the attack leader can lock the rally.

Available while the lead fleet is still traveling.
Once locked, no new allies can join.
Existing participants are unaffected.
Locking does not change the group ETA or force the battle to start early.

Use this when you are happy with the current lineup and want to stop late joiners.

ETA & Delay Logic

FCS synchronizes every fleet in the group to a single group arrival time. All members share the same ETA shown on fleet cards.

Key concepts

Term	Meaning
Initial lead arrival	The leader’s original ETA at launch. Stored permanently and used as the delay baseline.
Current group arrival	The synchronized ETA for the whole group. Can move later, never earlier than the current group ETA when someone joins.
Natural travel time	How long each fleet would take to reach the target on its own, from departure. Stored per fleet.

When an ally joins

new group arrival = max(current group arrival, ally's natural arrival from now)

A faster ally does not make the group arrive sooner.
A slower ally pushes the group ETA later so everyone arrives together.

Max delay settings

Set by the leader at launch:

Setting	Behavior
0 min	No delay allowed. If an ally cannot arrive by the current group ETA, join is rejected.
5 / 10 / 15 min	Group arrival cannot be later than initial lead arrival + that many minutes.
Unlimited	No cap on how late the rally can be pushed by slow allies.

Examples

Example A — faster ally joins

Group ETA: 12:10
Ally would arrive at 12:05
Result: Group stays at 12:10

Example B — slower ally joins

Group ETA: 12:00
Ally would arrive at 12:10
Result: Group moves to 12:10

Example C — max delay exceeded

Initial lead arrival: 12:00
Max delay: 5 min (cap at 12:05)
Ally join would push group to 12:10
Result: Join rejected

When a participant recalls

If an ally recalls while traveling:

They are detached from the group.
Group ETA is recalculated from remaining members’ natural travel times.
The ETA can move earlier if the slowest fleet left.

Battle start timing

The battle does not start when the first fleet arrives. It starts only when:

Every fleet in the group has reached its synchronized arrival time, and
All members are in traveling or onMission status.

Fleets that have arrived early wait until the full group is ready.

Recalling Fleets

Leader recalls

All participant fleets are automatically recalled (cascade recall).
The rally is cancelled.
Alliance is notified.

Participant recalls

Only that player’s fleet returns.
Group ETA is recalculated for remaining members.
The rally continues if the leader and other participants remain.

Combat Resolution

When the full group is ready, all attacker fleets are combined into one battle simulation.

Combined attack

Each participant’s ships fight together as separate attacker entries in the same battle.
Defender ships, stationed fleets, colony defenses, and hangar protection apply as in a normal attack.
War fatigue on loot is calculated from the lead attacker’s protection status against the defender.
If any participant cannot legally attack the target (e.g. protection rules), all fleets in the group are recalled and no battle is fought.

Attack protection & war fatigue

Loot reduction from war fatigue uses the leader’s fatigue multiplier.
If the defender suffers significant losses (5%+ ships/defenses or any loot taken), each participant may have the attack recorded against them for war-fatigue purposes individually.

Loot Distribution

On victory, total loot is calculated from the defender’s colony (subject to war fatigue and available resources), then split among participants.

Contribution score

Each fleet earns a contribution weight:

contribution = fleet power sent + damage done + cargo capacity

Where:

Factor	How it’s calculated
Fleet power sent	Sum of `(attack + defense) × ship count` for each ship type in that fleet
Damage done	Share of total attacker damage, proportional to that fleet’s fleet power
Cargo capacity	That player’s fleet cargo capacity (ships + bonuses)

Share formula

your loot share % = your contribution / sum of all contributions

Each resource type is allocated with floor() (rounded down). Small remainders may be left unassigned due to rounding.

Practical implications

Bigger, stronger fleets earn more loot.
Fleets that deal more damage earn more loot.
Fleets with more cargo capacity earn a larger share (even before cargo limits are applied on return).
On defeat, participants keep their original cargo (no loot gained).
If a fleet is destroyed in combat, its loot share is lost with the fleet.

Ship Loss Distribution

Attacker ship losses from the combined battle are split back to each fleet by ship type, proportional to how many of that ship type each fleet sent.

your losses of ship X = round(total losses of X × your count of X / total count of X)

Losses are capped so a fleet cannot lose more ships than it sent.

Each participant receives:

Their own battle report
Their own return fleet with remaining ships and their loot share
A push notification for victory or defeat

The defender sees one combined battle report with all attacker fleets merged.

Debris & Moons

Debris is generated from the combined battle as a single field (attributed to the lead fleet for harvest purposes).
Moon creation checks run on the defender’s planet as in a normal attack.

Limitations Summary

Topic	Limit
Mission types	Attack only
Allies per rally	Default 2 (server-configurable)
Fleets per player per rally	1
Who can join	Same alliance, same realm, not the leader
Join window	While lead is traveling and participation is not locked
ETA	Synchronized across group; joining can delay, never hasten
Solo open rally	If nobody joins, behaves like a normal solo attack
Notifications	Defender notified once (on leader launch)
Pirate targets	Supported; FCS battle flow applies

Quick Reference: Player Actions

Action	Who	When
Open rally	Leader	At attack launch
Set max delay	Leader	At attack launch
Join rally	Ally	While traveling & unlocked
Lock rally	Leader	While traveling
Recall (cascade)	Leader	Recalls everyone
Recall (solo)	Participant	Leaves rally, others continue

Glossary

Term	Definition
Lead fleet	The initiator’s attack fleet (`isParticipatable = true`)
Participant fleet	An ally fleet linked via `parentFleetId`
Group arrival time	Shared ETA for the entire coordinated attack
Rally	A coordinated attack with the alliance join option enabled
Lock rally	Leader closes the rally to new participants