Arthashastra
दुर्ग अर्पणः कोशो दण्डस् तूष्णीं युद्धं स्व पक्ष निग्रहो दण्ड बल व्यवहार आसार प्रतिग्रहः पर चक्र अटवी प्रतिषेधश् च ॥
for it is in the fort that the treasury and the army are safely kept, and it is from the fort that secret war (intrigue), control over one's partisans, the upkeep of the army, the reception of allies and the driving out of enemies and of wild tribes are successfully practised.
english translation
durga arpaNaH kozo daNDas tUSNIM yuddhaM sva pakSa nigraho daNDa bala vyavahAra AsAra pratigrahaH para cakra aTavI pratiSedhaz ca ॥
hk transliteration by Sanscript