Relating to War is the Book X of Arthashastra. It lays down the Shastra for war as it had been one of the most important functions of a state in ancient times. It was with wars only that a king could think of success in near future. As such it remained one of the most important concerns of Kautilya who with his book tried to lay down the principles as well as structure of warfare.
Relating to War discusses about encampment; march of the camps; protection of the army in times of distress and attack; forms of treacherous fights; encouragement to one`s own army; the fight between one`s own and enemy`s armies; battle-fields; the work of infantry, cavalry, chariots and elephants; battles with infantry, cavalry, chariots and elephants the array of the army like a staff, a snake, a circle or in detached order and others.
Relating to War explains that the invader along with his ministers makes sure of the survival contingencies available for his own army to with stand a long and strong battle. This includes looking into the provisions of building up of camps with either circular or square in shape. It then makes provisions to search out accompanied sources like villages, forests and roads which fall in the way of the marching of the army. As such precautions are to be taken for their security as well. Further the army was given a proper structure to march. Moreover, it remains the responsibility of the king to protect the army when it passes through adverse climate as in dessert or through forests with wild animals.
Relating to War further enumerates on various s forms of war which includes war with treacherous war tactics, encouragement to one`s own army and the actual fight between one`s own army and that of his enemies. It is expected that one who has succeeded in playing intrigues and one who bears a strong army and who has sort out ways to secure its army from danger and who has secured himself a strong position other than treachery is in a position to wage a war against its enemy.
Relating to War further lays down some of the conditions during which avenging a war would be most beneficial. It then talks of the battlefield itself and mentions the role of infantry, cavalry, chariots, and elephants separately in details. The role of an infantry and cavalry remains perpetual in an army as they are able to serve at any condition both in deserts as well as forests and high lands and lowlands.
Thus, relating to war which is the Book X of Arthashastra mainly centres itself with war structure and war methodology. Overall the detailed description of war methods which are mentioned in Arthashastra had set the base of ancient Indian war strategy which reflects the systematic administration of Maurya Empire.