Grass and firewood should be set on fire as far as a yojana (5 5/44 miles); water should be vitiated and caused to flow away; mounds, wells, pits and thorns (outside the fort wall) should be destroyed; having widened the mouth of the underground tunnel of the enemy's fort, his stores and leaders may be removed; the enemy may also be likewise carried off; when the underground tunnel has been made by the enemy for his own use, the water in the ditch outside the fort may be made to flow into it; in suspicious places along the parapet (of the enemy's fort) and in the house containing a well outside the fort, empty pots or bronze vessels may be placed in order to find out the direction of the wind (blowing from the underground tunnel); when the direction of the tunnel is found out, a counter-tunnel may be formed; or having opened the tunnel, it may be filled with smoke or water.