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Ships assigned to Defence Officer
Any ship fighter (S/M Fight ships) assigned to a station's DO will be used to patrol the local zone , sector or escort manager assigned ships. Due to how carelessly the DO will allocate the ships there is a fair chance that S and M FIGHT ships could be destroyed over time. Instead it is recommended the player manually allocate ships to certain defensive roles such as patrolling zones and guarding vulnerable ships. For station defense a combination of expendable drones and locally assigned patrol ships should sufficiently support the station defenses in case hostiles threatenor escort medium Trade/Mine ships assigned to Managers. If you assign new medium Trade/Mine ships to the manager, you'll need to relocate escorting fighters back to the DO if you'd like the DO to share them out again. Given their fragility, you are likely to have to assign new fighters to the DO on a semi-regular basis so beyond the early game-game, you may prefer to use capital ships instead (sturdier and self-repairing).
Capital ships assigned to DOs will only go on patrol in the zone (any capital, even if they have Trade/Mine/Build designation). If you'd combat-capital ships to escort Trade/Mine ships assigned to Managers, you'll need to do that manually. Ordering combat capital ships to patrol particular zones is another alternative.
An additional means of defending a station against hostile fighters is with combat drones, which can be replaced automatically via the Supply Options menu.