Semms like if you have a fort outside your cultural borders this replaces the normal 50% extra defence, that a fort gives inside your cultural borders.
From CIV4ImprovementInfos.xlm - Improvement Fort.
<AidTypes>
<AidType>AID_FORT</AidType>
</AidTypes>
Which calls this:
From CIV4AidInfos.xml - Aidtype for Forts:
<AidInfo>
<Type>AID_FORT</Type>
<Description>TXT_KEY_AID_FORT</Description>
<AidStyleType>AIDSTYLE_FIXED</AidStyleType>
<bCoastalOnly>0</bCoastalOnly>
<iRange>1</iRange>
<SupersedesAidTypes/>
<Promotions>
<PromotionType>PROMOTION_AID_FORT1</PromotionType>
<PromotionType>PROMOTION_AID_FORT2</PromotionType>
<PromotionType>PROMOTION_AID_FORT3</PromotionType>
<PromotionType>PROMOTION_AID_FORT4</PromotionType>
</Promotions>
<Button>Art/Interface/Buttons/Promotions/Fort1.dds</Button>
</AidInfo>
From CIV4PromotionInfos.xlm - promotion PROMOTION_AID_FORT1 to PROMOTION_AID_FORT4
<bTemporary>1</bTemporary>
Kind of "tells" me, that this promotion only is active under certain circumstances (my guess is that the unit actually
is placed - and maybe also fortified - on the same tile as the fort is to have this promotion active).
And below each of the single Fort_Aids (screenshots):
Above seems to give much-to-much extra defense to fortified units in a fort outside cultural borders. And what I do not quite understand are, how can a unit "use" withdrawal chances, no penalty for crossing rivers and extra first strikes since it dosn't attack - if it did, it would "leave" the tile that gave the fort-bonus..... wouldn't it?????
Question is:
Should some of the values be reduces and/or some of the unittypes removed
OR
Should early siege units somehow be added something like collateral damage?!?!?!
Don't know yet