Kautilya's Arthashastra 13.4.44

13.4.44

yad vā mitram āvāhayed āṭavvikaṃ vā, tam utsāhayet "vikramya samruddhe bhūmim asya pratipadyasva" iti //

Or a friend or a wild chief in friendship with the enemy may be induced and encouraged to seize the land of the enemy when the latter is besieged by the conqueror. When accordingly any one of them attempts to seize the enemy's territory, the enemy's people or the leaders of the enemy's traitors may be employed to murder him (the friend or the wild chief); or the conqueror himself may administer poison to him. Then another pretending friend may inform the enemy that the murdered person was a fratricide (as he attempted to seize the territory of his friend in troubles). After strengthening his intimacy with the enemy, the pretending friend may sow the seeds of dissension between the enemy and his officers and have the latter hanged. Causing the peaceful people of the enemy to rebel, he may put them down, unknown to the enemy. Then having taken with him a portion of his army composed of furious wild tribes, he may enter the enemy's fort and allow it to be captured by the conqueror. Or traitors, enemies, wild tribes and other persons who have deserted the enemy, may, under the plea of having been reconciled, honoured and rewarded, go back to the enemy and allow the fort to be captured by the conqueror.