Dr Adrian Goldsworthy

So it already looks like this is a bit of a damp squib.

You think back to King Agus of Sparta, others who've campaigned in 4th century BC, a lot in Asia Minor.

They've done a bit, they've sacked a few cities, they've kicked down a few doors, made a nuisance of themselves, but they've never required a big royal army to deal with.

Oh, for goodness sake, the Greeks are back again.

Yeah, and they go again.

So there's no particular reason to think this is going to be that different.

But your satraps take it seriously.

The problem is that they are, as Persian great king, you don't want your satraps to get too organized because one of the other truths of history is that the ones on the fringes tend to rebel fairly often.

So you don't appoint one as sole authority and say he can tell everybody.

So you've got basically a committee in charge, which is always a bit difficult, particularly when you need snap decisions in a military situation.

But you basically get the troops they have in their household, what they can raise locally.

And it's still pretty impressive.

You've got 10, perhaps even 20,000 cavalry.

You've got 20,000 or so infantry, a significant part of them Greek mercenaries fighting as hoplites.

Again, comes back to the problem you talked about before.

We get a terrific breakdown of Alexander's army, particularly the Macedonian bits of it.

We don't get the same for the Persians.

The sources are vague.

Some of the numbers are wildly inflated.

The emphasis here is on the diversity, the number of different ethnic groups within the cavalry is emphasized.