Wars, on large scale, are usually fought between factions/kingdoms/clans/etc, and, very importantly, together with the mods, who oversee and regulate the events that pass in war in order to make sure everything happens as fairly as possible, or to create unforeseen circumstances. The warring parties do not directly converse or rp with one another. Rather they pass on their tactics, initial army numbers, map movements, preparations, and more, to the Mods overseeing the war. This is done through Turn Based system. During every round, each warring party gets the chance to say what they are going to do. But more importantly they hear where, and how, if at all, they interacted with the enemy army or if they found out about the enemy army interacting with them (in the case of say a sneak attack.), or if actual conflict broke out. Conflict is discussed by one or three mods (Depending on size/availability), who will fairly assess things such as terrain advantage, army numbers, type of gear and equipment, and more, before calculating the losses for each side.
Rpc’s, and even npc’s, can also be involved with war. During each war there will be scenarios where one or several of such characters are fighting for one of the sides, or neither at all, sometimes even merely trying to escape the battlefield. During these scenarios there is a large chance at combat. In these combat encounters, the enemies will be played by the owner/member of one of the enemy warring factions. In these scenarios it's not uncommon to fight against large numbers, but when victorious you might draw out special enemies who are often infamous amongst soldiers.
!!Remember to make use of the mod’s presence. If you have any question regarding specifications in things such as distance, identification, or whatever may come to mind, just ask the mod. Normally you would have to ask the other roleplayer, which may lead to arguments, but now all you have to do is ask the mod who has the answer ready for you. If the mod doesn’t have an immediate answer he will get it from the other party. This means that you only have to focus on which commands you want to give to your army. !!