Xerxes Five Million Men

[hoplite14gr]

Two points about Napoleon's Russian Campaign:

He invaded in June; his retreat from Moscow began in October. He had lost the campaign before the winter began.

"Right from the beginning ill-health was to beset the mighty (Napoleon's) army. Diphtheria, dysentery and typhus, soon aggravated by malnutrition and semistarvation, would take a heavy toll. To cite one instance, the Bavarian Corps lost half its strength from sickness before it ever made contact with the enemy."

David Chandler, The Campaigns of Napoleon, "The Road to Moscow" pp. 758-9

Same thing with Xerxes. He started in the spring and he retreated in winter.
Salamis happened in 22 September. He had to cross back through places that his army had devastated. Sickness must have been more terrible because thought the civilised Persians might have better standarts the rest of the barbarian hord is not likely to had them.
Xerxes personaly might even have used a boat or a barge to cover more distance. But his army huge by the stndarts of the era, might have collpaed the same way the Grand Armee in the frosen steppes. Even today temperatures in the mountain passes of central Greece get a 25 to 30 below zero and troops passing the Neurokopi area on the way to Helespond might faced -40. Last year Kato Nevokopi scored -39 in January.
Kind regards