Analysis of information sources in references of the Wikipedia article "Camelaria" in Portuguese language version.
He collected together all the camels that had come in the train of his army to carry the provisions and the baggage, and taking off their loads, he mounted riders upon them accoutred as horsemen. These he commanded to advance in front of his other troops against the Lydian horse; behind them were to follow the foot soldiers, and last of all the cavalry. When his arrangements were complete, he gave his troops orders to slay all the other Lydians who came in their way without mercy, but to spare Croesus and not kill him, even if he should be seized and offer resistance. The reason why Cyrus opposed his camels to the enemy's horse was because the horse has a natural dread of the camel, and cannot abide either the sight or the smell of that animal. By this stratagem he hoped to make Croesus's horse useless to him, the horse being what he chiefly depended on for victory. The two armies then joined battle, and immediately the Lydian war-horses, seeing and smelling the camels, turned round and galloped off; and so it came to pass that all Croesus' hopes withered away.