You have a line of sight radius of two grids. Anything beyond the line of sight of you and your allies is in the fog of war. Armies inside the fog of war is not visible on the map.
Ambushes & Charges
Both the defender and the attacker may ambush his or her opponent in a forest. An ambush causes increased casualties to the army on the receiving end of the ambush. Ambushes may also sometimes occur when there is rain or snow. The chances of an ambush to succeed, depend upon the relative size of the army and the tactics trait of the general leading the army.
Both the defender and the attacker may charge on his or her opponent on plains. A charge causes increased casualties to the army on the receiving end of the charge. The chances of a charge to occur, depend on the relative size of the mounted units in an army and the tactics trait of the general leading the army.
Castles may increase the armor points of the units of the defender.
Your clan can conquer territory from other clans by claiming the capital of a Han, this is done by laying siege to that capital. Once a Han capital has been claimed all Shoen attached to that Han are conquered.