I know that the Greeks had a god of war and many other deities associated with warfare in some respect. I also know that the Greeks would consult the oracles for advice prior to their military endeavours. But what i am unsure of is whether there where any conflicts in the ancient Greek world which resembled closely the crusades of medieval times in terms of ideology and propaganda?
The only example i know of the top of my head is Alexander the Great's war against the Persians where he "exacted revenge" for their burning of the Greek temples:
"He also set the Persian palace on fire against the advice of Parmenion, who argued that it was ignoble to destroy what was now his own property and that the peoples of Asia would not pay heed to him in the same way if they assumed he had no intention of governing Asia but would merely conquer and move on. [12]But Alexander declared that he wanted to pay back the Persians, who, when they invaded Greece, had razed Athens and burned the temples, and to exact retribution for all the other wrongs they had committed against the Greeks. It seems to me, however, that in doing this Alexander was not acting sensibly, nor do I think there could be any punishment for Persians of a bygone era."
-Arrian: 3.18.11-12