How this code works?

[Huy1996]

Thanks, problem is solved.

 

[Gedemon]

you need to replace g_TunerSelectedPlayer by a playerID

 

[Gedemon]

I should have asked first: you want to use that code in the tuner or in a script in a mod ?

 

[Gedemon]

should work, keep the g_TunerSelectedPlayer and replace "local otherPlayerID = 1" with the ID of the other civ you want the selected civ to declare war with.