In 331 B.C., 250,000 Persian troops fought 40,000 Greeks under Alexander. Darius III had 40,000 horsemen in his cavalry alone. Through strategic positioning, Alexander went straight for Darius and forced him to flee with his troops following him now leaderless. The odds of victory were slim and yet it happened.
Darius wins the Battle of GaugamelaThe two-hundred year old Persian powerhouse does not fall and come to an end but would continue for many more years. Babylon wouldn't be pillaged over the next hundred years and perhaps the country is maintained through one ruthless leader after another up until the time of the Romans. Alexander, Son of Phillip, never becomes "Great" and his Macedonian empire crumbles under the existing weight of his father's debts.
Although many will say that Alexander's life was all for naught anyways due to an early death, it is hard to ignore the accomplishments of his life. Persia was the worlds superpower which had a larger army than any other county and outnumbered Alexander's army five to one.
A new story by Brian PeotterThe effect of Alexander's reign on the ancient world was a hurricane mixed with a tornado mixed with a wildfire. His legacy was studied by Hannibal, Scipipo Africanas, and countless other famous generals all the way to today's West Point graduates. Generals used the battle of Gaugamela as well as others to encourage their men(and themselves) in battles with overwhelming odds against them. The knowledge of this victory might very well have had an effect on other battles through the judgment of other generals.
This is not to mention the fact that the political geography of Greece would have changed the day after news of Gaugamela reached Greece. Athens and Sparta would become the new sources of influence in most of the country as Macedonia fell apart. Perhaps Rome has more trouble conquering Greece in the next century as there would have been more of a gap of time to redevelop a government and army within Greece. Persia too has a different outlook; instead of becoming a land of many kings and city states it might be the Persian empire standing up to the invading Roman army and perhaps Rome could fail to conquer the eastern Mediterranean.