Arthashastra
तस्मात् प्रभूत उदके देशे वर्षति च हस्ति बल प्रायो यायात् ॥
Hence, against a country containing plenty of water and during the rainy season, one should march with an army mostly composed of elephants.
english translation
tasmAt prabhUta udake deze varSati ca hasti bala prAyo yAyAt ॥
hk transliteration by Sanscript