Something else to know about 1.5 is that the difficulty level has a large effect on diplomacy.

If you are playing at the higher difficulty setting you are going to be facing self destructive homicidal maniacs.

Besides having massive cash bonuses so they field large armies (while you face some penalties) there is a player hating god to go along with the rest.

If you are just coming back to the game, try playing on Normal campaign difficulty.