Food supplies during Persian War again

[Jona Lendering]

The average ancient merchant ship, I read in Engels' Alexander the Great and the Logistics of the Macedonian Army, page 112, could carry 140 tons of grain. That is the solution to the problem I posted before (link from old RAT).

Assuming ...

• (1) that Xerxes took with him about 200,000 men, 8,000 horses, 20,000 carrying animals (cf. Peter Green, Greco-Persian Wars; other authors offer similar estimates)
  (2) that the chronology of Kenneth Sacks, "Herodotus and the Dating of the Battle of Thermopylae", in Classical Quarterly ns. 26 (1976) is correct (accepted in CAH; cf. [url:1eo5f4b5]http://www.livius.org/he-hg/herodotus/diary.html[/url])

... I think that ...

• (1) Xerxes' army needed 400 ton of food/day
  (2) Xerxes' navy needed 175 ton of food/day (650 trieres protecting 550 merchant ships)

... and I infer that ...

• (1) Xerxes could reasonably assume that he would be able to reach Athens within a month after leaving Therma (as in fact he did)
  (2) break through to the Peloponnese
  (3) create a new base (e.g., Cenchriae, Nauplion, Troezen)
  (4) send back his fleet and a part of his army
  (5) leave an army, with supplies for five months, to mop up resistance on the Peloponnese
  (6) send new supplies in the spring, when the Aegean Sea became navigable again

... if ...

• (1) He could gather about 77,000 tons of food in Therma
  (2) He could overcome the Greek navy (which was not very forthcoming)

These numbers (200,000 men; 550 merchant ships; 650 trieres; 77,000 tons of food supplies) are not impossible. The operation is about as complex as Nearchus' voyage from India to Babylonia.

Further comments are welcome.