Retreating is a special movement status that military forces may enter as a consequence of losing a battle, or more rarely, small size. A retreating unit cannot engage in battle, and the player cannot control a retreating unit.
Causes of Retreat
There are three possible causes of retreat.
Whenever any military unit's morale hits zero in combat, its side immediately loses the battle. All forces on the side are placed into retreat mode. When retreat is forced from battle, the destination province for the retreat is chosen automatically by the game.
A human player may voluntary retreat from a battle. In this case, the battle is still lost (for warscore purposes), and all allied forces in the battle will retreat. The retreat is generally the same, except that the destination province for the player's armies may be chosen by the player. You cannot always select certain provinces as a retreat destination. Generally you can always select your provinces with your troops in them. Other provinces may or may not work. If you want to retreat to a province and the retreat doesn't "take" on the first try, give it a few more clicks before you give up and select another.
AIs never choose retreat from battle. No matter how bad the odds, they will always simply fight until destroyed or forced to retreat.
It is often a good idea to retreat your own forces "by hand" when you're about to lose the battle anyway, because otherwise they'll often get retreat paths that are stupid and/or dangerous.
Inability to Cover
Whenever the combined size of all stationary friendly armies in an enemy-controlled province is too small to cover the province, all friendly forces will immediately retreat. This usually happens as a result of attrition during sieges.
Entering the Retreating Status
When a unit is forced to retreat, it will pick some adjacent province and plot a move to it. If the player has ordered the retreat, then his selected province is usually the destination province. However, not all valid provinces can always be selected.
Normal criteria used for movement apply: a unit cannot retreat to a province if it could not normally plot a move there. Retreating as a boarding move is allowed. If a land unit is forced to retreat but it has no adjacent province it can move to (including no fleet it can board), it is destroyed instead. The move is a normal move as far as the movement time is concerned. If the unit was moving towards the same province when it retreated, any old progress is lost.
The criteria for selecting the destination province when more than one are allowable are not completely known. A unit will never choose a province containing an enemy army (even if it is a tiny army) if there is any other province which it may move to. An army's country's own provinces are preferred to those of others.
Naval units can always retreat. However, land units cannot always retreat; for example if they are on an island and there is no friendly naval force with adequate passanger capacity in adjacent waters. In this case, voluntary retreat is impossible; if retreat is forced, the unit will instead be eliminated.
Effects of Retreating
While a unit is retreating, it cannot be engaged in battle.
While a unit is retreating, the player cannot give it movement orders, including stop-movement. The player may still disband it, which can sometimes be useful to prevent the warscore losses that it would otherwise accrue from being kicked around for many battles. He may also split it, although this is rarely advisable.
Leaving the Retreating State
When a unit arrives in the destination province, it will be removed from the retreating state. If a unit cannot complete the move, it will be placed into a strange ghostly state, where it is eternally retreating but never arrives. (Armies in this state do eventually go away, via attrition, although this requires decades.) An army cannot complete a retreat in two circumstances:
- it is retreating across a strait, which is blocked on the day it is scheduled to arrive
- it is retreating into an ocean (i.e., boarding), and there is inadequate passenger space available on the day it is scheduled to arrive.
You can sometimes arrange to exploit these rules. For example, Byzantium at game start often fights in a desperate war against the Ottomans; in this case, you often will want to risk letting a huge Ottoman army cross the Aegean in order to engage it in Constantinople with the defending on shore bonus. If you lose the battle, you quit the game. If you win, and you've placed armies correctly, the Ottoman army will be forced to retreat back across the strait, at which point you can destroy it simply by blocking the strait when it should arrive, a day which you can easily compute (see land movement times).