
Originally Posted by
mrtwisties
Strategically, they're both overrated.
At Issus, Darius led an army that had taken him mere months to assemble. Although they lost, the Persians retreated with the bulk of their better forces (cavalry, immortals, greek mercenaries) intact.
After Issus, while Alexander besieged Tyre and Gaza, the Persians (and their allies) counter-attacked on multiple fronts in the Peloponnese, Lydia, the Hellespont and the Aegean. Hardly the actions of an empire on the ropes.
(By sheer bad luck, all of these counter-attacks were defeated).
At Gaugamela, the Persians had a better prepared army. They again lost, perhaps more emphatically this time, but they again retreated with a fair number of their better forces intact.
After Gaugamela, Darius' resources were certainly more strained than they had been before. But the Persians were still able to fight a decent defensive war, buying time as Darius assembled a new force at Ecbatana. I think it took something like 30 days for Alexander to force his way through the Persian Gates, for example. Obviously, it wasn't exactly ideal having a conqueror traipsing through the heartland of the Persian Empire - but there's every indication that Darius was starting to assemble a decent-sized force at Ecbatana when he was betrayed by Bessus.
It was Bessus' betrayal that really put an end to Persian opposition. Remember, the Persian Empire had been roiled by in-fighting and secession before Darius took over as Great King just a few months before Alexander became King of Macedon. It was actually pretty impressive of Darius to hold the empire together the way he did, and it seems he was able to draw on a fair bit of charisma and energy to do so.
When he was betrayed and imprisoned, the intriguing factions were presented with a choice - either ally themselves with Bessus the usurper, or with Alexander the successful chap who had a track record of treating Persian nobles decently. It was at that point that the empire unravelled.
But if Darius had not been betrayed, the Persian Empire could have fought on. Perhaps they would still have lost. The Macedonian war machine was pretty impressive, and their generals were both talented and experienced.
But it wouldn't necessarily have turned out that way. Many times in history, Iranian empires have "pulled a Russia" on western land armies. Earlier in the campaign, before Granicus, Memnon had advocated doing just that. If Darius had remained in charge and retained the loyalty of the populace, Alexander's supply lines would have been far less secure. How far east could he realistically have marched? Who knows how things could have turned out?
So I don't think Issus and Gaugamela were as significant as most textbooks seem to think they are. Great battles, certainly, but they didn't bring about the downfall of the Persian Empire.
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