Defines.txt
From EU3 Wiki
This is an interresting file that should be modified with caution. It defines most of the constants that usually are hardcoded. This means that you have the option to change these values as well. We will not go into a full discussion on all the values here yet, but will list a few examples:
1000 #GARRISON_SIZE
This defines the garrison size added for each fort level. If you wish to play without forts, you could try setting this to 0.
1.0 #MDEF_INFANTRY_SPEED_, 1.5 #_MDEF_CAVALRY_SPEED_, 0.75 #_MDEF_ARTILLERY_SPEED_,
Here we have the movement speed for the three main unit classes. You can change the ratio between them and make them faster/slower.
2.0 #_MDEF_MERCENARY_MAINTENANCE_
This defines the maintenance cost for mercenaries. By default they are twice the cost of regular troops.
50 #_CDEF_CORE_LOSE_, //50 25 #_CDEF_CORE_GAIN_, //25
This defines the year limits on dynamic cores, how long you will keep a core before losing it and how long you must hold a province to gain a core.
1000 #_DDEF_DEFENDER_OF_FAITH_COST_
This defines the Defender of faith cost. By default they are 1000.
Modding defines
Many of these definitions are a bit cryptic, and the exact effect ingame is not known. Editing may require a lot of testing to get it right...

