Uhm... Robert? Are you forgetting that little thing called the Persian Empire, which Alexander just smashed apart like matchsticks? It also fielded massive armies of hundreds of thousands of men. And the Immortals, the 10,000 elite cavalry (not all the cavalry, just the elite) were (and are) widely regarded as the most powerful cavalry of the day, before Alexander's Companion Cavalry came along.
You are seriously underestimating the brilliance of Alexander the Great here. I've noticed a really bad tendency on this board to go the opposite of most people; for example, whereas most people who have heard of Alexander say "he was the greatest general ever" (or some such), quite a few of the people here will go the complete opposite route, arguing that he wasn't that great a general (I've seen this done for Julius Caesar, Napoleon Bonaparte, Erwin Rommel, etc.). While it's true that people should be objective and that NO ONE is invulnerable, you really can't expect something like "he won every battle he ever fought, but had he continued he would have lost his NEXT ONE VERY BADLY" to be taken seriously. Alexander marched across the vastest empire in the world, fighting armies many times larger than his a good 3 times, and annihilating each one. Give the guy a LITTLE credit, at least!
My view of it is that Alexander earnestly believed he had reached very close to the end of the world; had he crossed the mountains and realized that another subcontinent (as well as the might of China, divided as she was) lay ahead, he would have realized the world is much larger than he had previously believed. Thus, he returns with his weary troops to rest and rebuild; having missed whatever specific virus it was that would finally fell him, Alexander sets off some 6 years later with an army nearly three times as large as the one he used to conquer the Persian Empire, trained in the tactics and formations that made him the ruler of the largest nation in the history of mankind. In the meantime, he fathers a son, Phillip, and has gained the acceptance of the Persian people as the new Shahanshah. His troops quickly mop up the Indian subcontinent, and he adds the title of Rajah to his already impressive resume. He works hard to ingratiate himself to the Indians, and their strict caste system allows for an absolute ruler, as he does not try to enforce his own religious beliefs onto the people.
Alexander's entry into China would be called the Wrath of the Southern Devils, and for centuries afterwards, the Chinese would speak of long-speared demons from the West. The elite phalanx formation of Alexander is a tactic that the Chinese have not yet encountered, and China, weary from years of internal warfare, is hard pressed to fight the might of the world's largest empire led by the world's greatest tactician. A courtier presents Alexander with copies of China's collected works; among them is a tome entitled "The Art of War." Intrigued, Alexander orders a Persian translation, as no one can yet speak both Greek and Chinese, and is astounded by the insights of this Chinese man named Sun Tzu. Already a fearsome opponent, Alexander further hones his skill, and always carried a copy of "the Art of War" with him onto the battlefield.
Alexander finally stops after conquering the kingdom of Qu; his empire is the vastest in the world, but he is now 50, having spent almost all of his adult life on the battlefield. Finally feeling age for the first time, Alexander rides back to Babylon; during the campaigns (which, altogether, have lasted some 11 years), his young son has grown into a strong youth, having ridden out during Alexander's campaign to join him after the conquest of India. The boy is now 16 and strapping, and Alexander announces him to be his heir and the next Ruler of the World.
Alexander dies peacefully in his sleep at the age of 56; from across the known world, humanity mourns the loss of its ruler. When Phillip takes the throne as Phillip III, he quickly proves to be as smart a ruler as his father, rooting out those among the generals whose loyalty to the Great King has not passed to his son and sending them back to Macedonia without their armies. All organized factions in the world have crumbled before the might of Alexander; his son, now, sits upon the highest throne in the world, ruling mankind.
