दुर्गाभावे च कोशः परेषाम् ॥ कZ_०८.१.३९ ॥
durgābhāve ca kośaḥ pareṣām
А при отсутствии крепостей казна попадает в руки других (врагов).
They show a trade-off: treasury is portable (enabling retreat), yet also needs fortified protection; forts secure wealth, but wealth enables mobility and continued resistance.