Empire: Total War - Game Mechanics - Diplomacy - Wars and peaces - game guide, walkthrough, secrets, game tips & strategies

In most cases, player is the person who is declaring war. You can do it on paper but it doesn't make any sense. You can do it only when you want to improve your relations with another country (“declare war to my friends enemy”).

The best option is to declare war simply by the attack on the enemy territory. Your opponent will not have enough time to strengthen his boarder forts. Moreover, if you will take some provinces quickly this may result in riots in the enemy capital city (reaction for the lost fights).

Sooner or later most the world will hate you for the territory expansion. There is nothing wrong with that. The goal in most of the campaigns is to conquer some new areas. It is normal that some countries will be scared.

In the higher levels of difficulty other countries can declare a war to you. Especially when they will notice that some of provinces are unsecured. The peace can be achieved in two ways: you may pay a tribute or simply defeat your enemy on the battlefield. In most cases peace is a matter of two battles or one province.