Alexander the Great's campaign to topple the Persian Empire seemed to have a great deal of propaganda supporting it. On multiple occasions he is said to be doing it to free the Greeks, or to get revenge on the Persians for Xerxes' campaign. How did this message impact Greek mercenaries in the armies of Darius and his satraps? It appears that Alexander encountered a few Persian forces of which Greek mercenaries played a large part, so was his notion of a panhellenic crusade really even effective, or did it just attempt to provide justification on his end?
Alexander was particularly harsh to Greek mercenaries and he even killed a large portion of them following his victory over them at the Battle of Granicus. This harsh treatment is said to have stiffened resistance against Alexander as Greek mercenaries under the Persians did not want similar treatment. Alexander also forced cities that surrendered to him to pay the same tribute that the Persians demanded so many Greeks that did convert to his side didn't see him as a saviour as they were treated similarly (or worse) than the Persians had treated them. It is also well documented that Alexander didn't like any of these conquered Greeks to object to his rule and he was not scared to intervene in local politics to enforce his will.
Tack on question. How Greek was Alexander's empire exactly and how did his Macedonian heritage influence it? What roles and functions did the other Greek city states and peoples fulfill in Alexander's empire?