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Revision as of 14:42, 23 July 2014 by Ius (talk | contribs) (Maintenance: created Supply ships reach)
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This page deals with the recruitment and maintenance of navies. For naval combat mechanics see naval warfare. For details about ship types see naval units.

A navy refers to a country's naval (sea) forces.


The basic unit of naval forces is predictably the ship. Each ship is classed as heavy, light, galley or transport.

Ships are grouped into fleets. Each fleet can be led by an admiral or explorer. A fleet travels at the speed of its slowest ship, so mixing different types of ships in a fleet in inadvisable, unless the stronger ships act as escort for weaker ships, for example, Transports.


Ships, unlike land units, do not upgrade in line with technology. Instead, they remain the same 'class' or 'model' that they were built as. This means that to remain a relevant naval power, you will have to replace ships on a regular basis as your diplomatic technology increases, unlocking new models.


Each ship costs ducats to upkeep every month. The amount depends on the type of ship and is proportional to the cost to build the ship, so reductions in ship cost will also reduce maintenance. Naval maintenance is computed as follows:

 naval maintenance cost = base cost * base maintenance modifier * (100% + build cost modifiers) * (100% + naval maintenance modifiers from tech) * (100% + naval maintenance modifiers not from tech)
  • Unlike land units, the tech modifier to Naval maintenance stacks multiplicatively with other modifiers. Thus, reductions to Naval Maintenance keep their strength better throughout the game than their land counterpart.
  • The Grand Shipyard building reduces ship cost and thus maintenance of ships built there.
  • Being over Force Limit will multiply the maintenance cost of ships by the force limit proportion. For example, being at 150% of the force limit will result in maintenance being 150% of normal.
    • For a homogeneous fleet, the marginal maintenance of each ship is about twice the force limit proportion. For example, being at 150% of the force limit will result in the next ship adding about 300% of its normal maintenance.
    • Light Ships suffer the penalty to their build cost as well, which squares the effect on maintenance cost. For example, being at 150% of the force limit with all Light Ships will result in maintenance being 225% of normal.
    • In this case, the marginal maintenance is about three times the force limit proportion squared. For example, being at 150% of the force limit with all Light Ships will result in the next light ship adding about 675% of its normal maintenance.

Supply ships reach

Supply range can be extended by the third idea in the Trade idea group.

Merchant Adventures Trade range.png+25% Trade range.

Also many trade focused nations have a national idea with a percentual trade range modifier. Note the stress is on a relative modifier. Technology, for instance, only increases the trade range by a fixed number and therefor does not influence the supply range length.

Another way to arrange for a favorable supply range is by gaining fleet basing rights from a nation in the vicinity of where attrition is undesired and/or ship repairs are needed.

The supply range is a key factor in determining whenever light ships can be sent to protect trade.


Navies suffer from attrition from being in the open sea or away from port too long. A navy does not suffer attrition if it is within supply range. The following factors influence attrition:

  • Base attrition (+1)
  • Time at sea (+1 per month, eliminated after Diplomatic tech level 22 is discovered)
  • Open sea
  • Whether a naval military leader is in command (admiral or explorer)

Note that AI navies do not take attrition as the AI is unable to adequately manage naval attrition.


Navies with ships that have sustained damage will automatically repair when docked in an owned, allied, or in a province with fleet basing rights.

To expand on:

  • Automatic docking for repairs
  • Rate of repair
  • Repair at sea

See also