Which was alexanders first major conquest?

Answer 1

Alexander began his reign by having his potential rivals to the throne murdered. After reconfirming Macedonian rule by quashing a rebellion of southern Greek city-states, Alexander launched a short but successful campaign against Macedon's northern neighbours. He was then able to turn his attention towards the east and the Persians. In a series of campaigns lasting 10 years, Alexander's armies repeatedly defeated the Persians in battle, in the process conquering the entirety of the Empire. The first victory over the Persians was the Battle of the Granicus.