I've seen quite a few of these debates online and Alexander the Great is usually occupying the top spot. However, I really don't believe he deserves to be there. His new modern professional army was built and blooded by his father's campaigns against the Greeks and Illyrians. I don't think anyone can argue that a major factor in his victories was his army and the technology they deployed against an old, outdated Persian Empire. Mix in the fact he had some of the greatest generals to grace the Ancient world in Craterus, Antipater, Perdiccas, Ptolemy, Lysimachus, Peucestas, Peithon, Leonnatus, Antigonus, Nicator just to name a few his achievements are no longer his alone to claim. His campaign in India and the Hindu Kush was in many ways successful but it was a bit of a shambles really and finally, the treatment of his troops and the disdain he had for them for me makes me question his number one spot. I personally think he gets credit for a lot of other peoples work especially his father Phillip of Macedon who doesn't get enough credit. Interestingly I have found a slight parallel in Caesars life in regard to the modernisation of the Roman army by Gauis Marius and again he was lucky to have a handful of extremely competent generals alongside himself.