Unfortunately there is a paucity of contemporary sources detailing the tactical operations of the Imperial Gupta Army. The best extant information comes from the Sanskrit mahakavya (epic poem) Raghuvaṃśa written by the Classical Sanskrit writer and dramatist Kalidasa. Many modern scholars put forward the view that Kalidasa lived from the reign of Chandragupta II to the reign of Skandagupta and that the campaigns of Raghu – his protagonist in the Raghuvaṃśa – reflect those of Chandragupta II. In Canto IV of the Raghuvamsa, Kalidasa relates how the king's forces clash against the powerful, cavalry-centric, forces of the Persians and later the Yavanas (probably Huns) in the North-West. Here he makes special mention of the use horse-archers in the kings army and that the horses needed much rest after the hotly contested battles. The five arms of the Gupta military included infantry, cavalry, chariot, elephants and ships. Gunaighar copper plate inscription of Vainya Gupta mentions ships but not chariots. Ships had become integral part of Indian military in the 6th century AD.