Yep, you could place a faction switcher as those boxes that change zone name (like in tutorial), or you could simply link a new key or touch icon to a peace/war mode (on key pressed, if it is war mode, change to peace mode, if in peace mode, change to war mode) with a further check about the player being in a scene where he could actually do it (like a neutral town, i wouldn't want my player to stay unharmed inside a dungeon). :)