Answer :

alexander built up a strong army and used new and innovated tools to take over. he also took over at a time when a lot of greek people had died of a disease and the government was corrupted.

Alexander The Great as he was known, was and excellent, sophisticated military leader considered by many historians as a genius.  Thanks to his greatness, Alexander the Great was able to practically changed the nature of the ancient world by himself in less than 10 years.

When he was in front of his armies he commanded them by example. The fact that he considered himself to be indestructible made him gamble, and  take extreme risks with his own life as well as the soldiers he lead.  

He was born in July of 356 BC in  the city of Pella which was the capital of Macedonia at the time. Also and most importantly,  he was educated by the great philosopher  Aristotle. After his father assassination Philip II in 336 BC, young Alexander took control of the kingdom his father left. Unfortunately, the kingdom was in a very precarious and volatile situation which he quickly was able to put under control by defeating all of those who opposed him at home. Later, he went on to conquer and control the entire Persian Empire.

Thanks to all of these attributes of courage, ingenuity and self confidence,   Alexander the Great was able to control and maintain a firm grip on Greece and the whole Persian Empire.