The correct answer is - before he defeated Darius III.
By 332 BC, the Macedonian Empire led by Alexander III of Macedon (Alexander the Great) still hadn't reached its heights, but it was on the right way to do so.
By this period, the Macedonian Empire managed to defeat and incorporate in its territory its arch rivals in the region, the Greek city-states, part of Iliria, Thrace, conquered Asia Minor in the initial battles with the Persians, the coastal parts on the Mediterranean in its westernmost part, and Egypt.
The final battle with the Persians led by Darius III was yet to come, with the final defeat of the Persians coming two years later, in 330 BC.