Today I scrambled through saved assignments from my school time and found an assignment I did in 7th grade about Alexander the Great (Basileus of Macedon). He conquered all of Persia and was the ruler of Macedon, an kingdom mostly based in Greece around 800-100 BC.
However, it got me thinking, what is/were the most powerful army of all time? Alexander the Great's army is the best to me, followed by probably the Mongol Empire. Just look at the losses in the Battle of Gaugamela.