Kautilya's Arthashastra 12.5.26

12.5.26

janapadam ekasthaṃ vā ghātayitum amitrānīkam āvāhayet //

Having access to the enemy's castle, the officer in charge of the boundaries (of the enemy's country) may lead a part of his force and slay the enemy in good faith under the plea of destroying a people in some place, he may take the enemy to an inimical army; and having led the enemy to the surrounded place, he may slay the enemy in good faith.