Kautilya's Arthashastra 13.4.55

13.4.55

eṣa prathamo mārgaḥ pṛthivīṃ jetum //

Having thus seized the territory of the enemy close to his country, the conqueror should direct his attention to that of the madhyama king; this being taken, he should catch hold of that of the neutral king. This is the first way to conquer the world. In the absence of the madhyama and neutral kings, he should, in virtue of his own excellent qualities, win the hearts of his enemy's subjects, and then direct his attention to other remote enemies. This is the second way. In the absence of a Circle of States (to be conquered), he should conquer his friend or his enemy by hemming each between his own force and that of his enemy or that of his friend respectively. This is the third way.