AWA283 - Why did the Macedonian phalanx struggle against the Greek mercenary hoplites at Issus?

Murray answers this question from Jsoth, 'during the battle of Issus, it's my understanding that the Macedonian phalanx struggled and even lost ground against Darius' mercenary Greeks. I was under the impression that if facing off directly, the sarrisa-wielding phalanx would be at an advantage with their longer spears, but here, that doesn't seem to be the case. Do historians believe this is accurate, and if so, why or how?' Join us on Patron patreon.com/ancientwarfarepodcast