Naval warfare

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Naval warfare is the competition of sea-going power between nations at war. While a majority of warfare is land-based, the naval aspect of conflict can be incredibly influential in the spheres of trade and conquest.

Naval units[edit]

In Imperator there are six different types of naval unit.

Unit type Cost Time Monthly Cost Requirements Naval
Unit liburnian.png Unit trireme.png Unit tetrere.png Unit hexere.png Unit octere.png Unit mega-polyreme.png
Unit liburnian.png Liburnian 5 120 0.08 Free 13 -15% -25% -35% -40% -50%
Unit trireme.png Trireme 8 180 0.13 Free 12 +15% -10% -10% -20% -20%
Unit tetrere.png Tetrere 10 180 0.16 Wood 12 +25% +10% -10% -10%
Unit hexere.png Hexere 15 180 0.24 Wood 11 +35% +10% +5% -10% -10%
Unit octere.png Octere 25 180 0.41 Wood, Military tradition 9 +40% +20% +10% +10% -10%
Unit mega-polyreme.png Mega-Polyreme 32 365 0.53 Wood, Military tradition 7 +50% +30% +20% +20% +10%

The fleet[edit]

The main purpose of a fleet in Imperator is to ferry troops from one destination to another, and to stop others from doing the same in your territorial waters. 1 ship can transport 1 unit of cohorts (with fully regained cohorts 1000 men) Fleets can also blockade ports in wartime, decreasing commerce and potentially contributing to the warscore for their side of the conflict. Futhermore fleets in a sea zone with a strait will block enemy units from crossing that strait.

Building a fleet[edit]

Ships can only be built in ports, and ports only exist in predefined locations around the map. Building ships other than Liburnians and Triremes also requires access to Wood in the Province that the City belongs to.


Combat is very similar to Land_warfare. The major differences are:

  • Strength damage is higher than with land combat so ships more likely sink in the combat.
  • Defeated ships have a chance to get captured.


Ships have a chance to be captured when they are defeated. There are 3 different cases:

  • Morale runs out: This is the normal scenario. The capture chance is based on ship categories and the enemy general.
  • Strength runs out: Same thing as above. However the ship gets destroyed even if it gets captured (resulting in multiple losses in the after battle screen).
  • Stack wipe: Result of enemy being greatly outnumbered or getting defeated very quickly. The capture chance from the enemy ship category is replaced by a fixed chance. Any ships captured during the combat will be returned to the enemy.

Sources of capture chance (all sources stack additively):

Type Amount Description
Base +6% The global capture chance. Military window shows that the base chance is 5%. In-game tests resulted also in a hidden 1% base chance.
Stack wipe +20% Stack wiping doesn't involve combat so enemy ship category can't be used. In-game tests resulted in a 20% increased capture chance.
Capturing ship category +10% per category Capture chance is increased 10% for light ships, 20% for medium ships and 30% for heavy ships.
Captured ship category -10% per category Capture chance is decreased 10% against light ships, 20% against medium ships and 30% against heavy ships.
General martial +0.2% * martial Martial skill of the general slightly increases the capture chance. For example 10 Martial gives a 2% increased chance.
General trait Sea Dog +10% Sea Dog trait increases the capture chance.
Boarding Tactics +10% Selecting the Boarding Tactics ability increases capture chance at the cost of reduced damage.


  • Light vs Light, with level 10 martial. 6% + 10% - 10% + 0.2% * 10 = 8% capture chance.
  • Light vs Medium, with level 10 martial. 6% + 10% - 20% + 0.2% * 10 = -2% capture chance.
  • Medium vs Heavy, with Boarding Tactics. 6% + 20% - 30% + 10% = 6% capture chance.
  • Heavy vs Heavy, with stack wipe. 6% + 20% - 30% = -4% capture chance.
  • Light vs Heavy, with stack wipe and Boarding Tactics. 6% + 20% - 30% + 10% = 6% capture chance

Unit abilities[edit]

There are unit abilities for ships at sea:

  • Ramming Tactics: Naval damage done +10%, Naval damage taken +10%
  • Boarding Tactics: Naval damage done -10%, Naval capture chance +10%
  • Raid Port: Steals a number of pops from an adjacent port and turns them into Slaves in your capital (at a cost of 1 Aggressive Expansion).

Domestic policy Characters Attributes Culture Government Laws National ideas Rebellion Religion Technology
Economic policy Buildings Economy Population Trade Trade goods
Provinces Region Province Cities Colonization
Warfare Military traditions Army Siege Assault Land units Land warfare Naval warfare
Foreign policy Treaties Casus belli Diplomacy Subject nations