When fighting in a war, your strength is the fundamental factor that determines the amount of damage you inflict upon your enemies. It is multiplied by your weapon's quality, your wellness, and then doubled as a bonus. (More...)
Using a weapon will improve the damage given to your opponents during war. When fighting barehanded, you can only do half as much damage as you normally would, so it is wise to carry a weapon of as high of quality possible into the battlefield.
After you fight for the first time in a day, the Battlefield will display the "Hospital" button, which will direct you to the region page. Hospitals can only be purchased with the proposal of the president of the country and with Congressional approval. (More...)
Resistance wars are wars started in conquered regions in order to liberate them from the occupying nation's control. If you are in a region that doesn't belong to it's original country, you may start a Resistance War if you have fought in the past and have the amount of gold required.