During Achaemenid times, the Persians would often pay good money to hire Greek hoplites into their armies. Xenophon writes that when Cyrus the Younger was showing off his brand new army to his lover he asked his hoplites to drill.
This order was repeated by the generals to their men; and at the sound of the bugle, with shields forward and spears in rest, they advanced to meet the enemy. The pace quickened, and with a shout the soldiers spontaneously fell into a run, making in the direction of the camp. Great was the panic of the barbarians. […] Cyrus was pleased to see the terror inspired by the Hellenes in the hearts of the Asiatics.
Anabasis, Book I – Xenophon
It is said that in battle, Persians would fight till the last Greek mercenary. I can see where that joke comes from.
Persians made the critical mistake of not writing down their history, and so most of what we know about them comes from Greek writers who spared no detail in highlighting how superior were Greek hoplites over barbarian armies. They were naturally biased, however stories of barbarian armies fleeing at the sight of drilling Greeks were rather common. The Siege of Pelium was another good example of that.