So in 332 BC Darius III wrote Alexander the Great a letter of friendship. Basically he gives Alexander everything west of the Euphrates on a silver platter and asks Alexander to marry his daughter to ensure peace and alliance.
In OTL Alexander gives him the Macedonian Middle Finger and goes to India. What if he was feeling happy that day when he woke up and accepted. While this means no conquest to India, this probably means Alexander lives longer, maybe even opens further conquests into North Africa, Europe, or Arabia?
What happens?