War at Sea

Fleets that fight their own battles: postures, commanding fleets, sea battles, blockades, convoys and escorts.

Beta channel only. This system is not in the stable release yet. To try it, install the beta build, which installs alongside the stable app and keeps its own saves.

On beta, fleets at war fight their own battles. The game decides them day by day over the period a time skip covers, the same way it fights the land war on battlefields, and the story is told what happened, at no extra request. A blockade that stands now costs the country it is laid on its trade, its economy and the strength of its armies. On the stable build a fleet is a formation like any other, and what happens at sea is whatever the story says: see military and combat.

The war at sea is part of the Fronts feature: switched off in a scenario's or a game's Features tab, fleets fight only when the story says so.

Fleets

A fleet is a naval formation on the map, as before: a strength, a make-up such as "carriers, destroyers and submarines", and a posture. What a fleet does at war is read from two things it already has: where it is, and its posture.

Commanding your fleets

Give a fleet its orders in plain words as an action, "Send the Pacific Fleet to blockade Japan", or, while you have troops on a battlefield, from the War Room: the rail's Fleets key puts out a plate beside the map. Pick a fleet from the list (each with its strength and what it is doing), then:

• Posture: Patrol, Blockade, Seek battle, Hold, Withdraw or Escort.
• Orders: Sail to or Patrol at a place at sea you then click on the map, or Call off its standing order.
• Blockade a country: pick a country you are at war with and press Blockade. The fleet sails to the water off that country's coast nearest it and closes what of its trade comes by sea there.
• Escort a convoy: pick one of your transporters at sea and press Escort. The fleet joins it from the middle of what is left of its way.

The panel's Fleets list shows each fleet's strength, posture and how far it has to go. A fleet just raised joins your order of battle when time next passes and takes orders then. As with everything in the War Room, orders are carried out when time next passes.

Countries nobody plays choose their fleets' postures by playing the period ahead out with each and keeping the best, unless the story gave a fleet its orders.

Sea battles

Hostile fleets within reach of each other may fight. Their reach grows with the era:

Each day there is a chance they meet: the keener either fleet's posture, the likelier. A fleet that is withdrawing is hard to bring to battle, and one withdrawing or holding within 120 km of its own coast is sheltered as well. A storm at sea makes a meeting a quarter as likely.

Every fleet of the two sides in reach joins the battle. Each side weighs what its fleets' strength, their countries' navies and their postures bring, and the side outweighed loses more. Afterwards:

• a fleet left at 10% strength or less is sunk and gone;
• a fleet under 35% breaks off and withdraws, and so does every fleet of a side that brought less than 42% of the weight;
• a fleet that has fought is in no state to fight again for 21 days.

A marker on the map shows where each battle was fought: a ring and a cross in the colour of how it went for you, with who fought and when beneath. Battles stay on the map for two turns, the older turn's fainter.

Blockades

A fleet in the Blockade posture, not beaten off and within reach of the coast of a country it is at war with, presses on that country. How hard, from nothing to a full blockade, is worked out for every day: how much of its coast the blockading fleets close, less what its own fleets and its allies' fleets in reach tie down, and by how much the country lives by the sea. An island lives by nothing else; a country with open land borders to neighbours it is not at war with lives by the sea less. A coast whose water has frozen counts as closed. A blockading fleet in a storm counts half.

What a blockade does:

• The economy. At full pressure a country loses 20% of its GDP over a year, and 6 points off its budget's balance; less in proportion to the pressure. What its forces have to spend falls with it.
• The land war. A country cut off from the sea runs short, fully once the blockade has stood for 90 days. Its armies on the battlefields come back up to strength more slowly, with fewer reserves, and fight and move a little worse. A blockade laid this period bites on land from the next.
• War resources refill more slowly, and war weariness rises. See relations, treaties and war.

On the map a blockading fleet has a dashed ring over the water it closes, and under it each country it presses on with how much of that country's trade is cut, as a percentage.

Convoys and escorts

Troops carried by sea from the War Room's Transport tool, or by the story, travel as convoys. Enemy fleets and aircraft in reach of their way can catch them, and a convoy that is caught loses troops or is lost. An enemy transporter on its way to your battlefield is listed in the War Room with Go after it, which sets your forces hunting it. A fleet given Escort for a convoy of yours shields it and saves part of what would be lost.

A navy for every coast

A country at war that has a coast, no fleet at all and an enemy it could meet at sea is given one, unless its military figures give it no navy: the Home Fleet, named for the country, patrolling its home waters, stronger for a stronger country. It is fitting out for its first 10 days and fights nobody. A country given a navy, or one whose last fleet is sunk, is not given another for three years.

Next

• The War Room — battlefields, troops and the Fleets plate.
• Military and combat — formations, posture and travel at sea.
• Relations, treaties and war — weariness, peace and alliances.

Open Historia is under active development on two channels, and this wiki is written by hand — a page can fall behind a release. Last checked against the game on 2026-10-25 · main 6e6239c4 · beta d7e8fa85. If something here does not match what you see in the game, trust the game and say so on Discord.