Arthashastra
अपकृष्ट स्कन्ध आवाराद् उच्छ्रित ध्वज धन्व आरक्षो वा मानुषेण अग्निना पर दुर्गम् आदीपयेत् ॥
If the camp is situated at a distance from the fort and is provided with an elevated post for archers and their flags, then the enemy's fort may be set on fire.
english translation
apakRSTa skandha AvArAd ucchrita dhvaja dhanva ArakSo vA mAnuSeNa agninA para durgam AdIpayet ॥
hk transliteration by Sanscript