Before Greek conquest, the armies of Bactria were overwhelmingly composed of cavalry and were well known as effective soldiers, making up large portions of the Achaemenid cavalry contingents. 2,000 Bactrian horsemen fought at the Granicus against Alexander and 9,000 at the Battle of Gaugamela on the left flank of Darius' army. Herodotus also mentions the widespread use of chariots among the Bactrians. After Alexander's conquest of Bactria, Bactrian cavalry units served in his army during the invasion of India and after the Indian campaign, Alexander enlarged his elite companion cavalry by adding Bactrians, Sogdians and other east Iranian cavalrymen. Both Aeschylus (The Persians, v. 318) and Curtius mention that Bactria was able to field a force of 30,000 horse. Most of these horsemen were lightly armed, using bows and javelins before closing with sword and spear. Herodotus describes the Persian cavalry of Mardonius at the Battle of Plataea (which included Bactrians) as horse archers ("hippotoxotai"). Bactrian infantry is described by Herodotus as wearing caps in the Median style, short spears and reed Scythian style bows.