Herodotus has documented that the Qedarites were called upon to assist Cambyses II of the Persian empire in his invasion of Egypt in 525 BCE. The Qedarites and Nabataeans were known to enjoy close relations, even engaging as wartime allies against the Assyrians. It is possible that the Qedarites were eventually incorporated into the Nabataean state which emerged as the strongest Ishmaelite presence in northwestern Arabia c. the 2nd century CE. In The Cambridge Ancient History, some of the (Arab) Nabataeans mentioned by Diodorus in his retelling of events that took place in 312 BCE are said to be Qedarites.