विस्मृते सुरुङ्गया रात्रौ राजावासमनुप्रविश्य सुप्तममित्रं हन्यात् ॥ कZ_१२.५.४४ ॥
vismṛte suruṅgayā rātrau rājāvāsam anupraviśya suptam amitraṃ hanyāt
When vigilance has lapsed, by a tunnel at night, having entered the royal residence, he should kill the enemy while asleep.
Continuously audit subterranean access, guard routines, and ‘lapses’; the greatest vulnerability is predictable negligence rather than overt force.