Kural - 744

A fort must need but slight defence, yet ample be,
Defying all the foeman's energy

Explanation
A fort is that which has an extensive space within, but only small places to be guarded, and such as can destroy the courage of besieging foes.

Tamil Transliteration
Sirukaappir Peritaththa Thaaki Urupakai
Ookkam Azhippa Tharan.