Here is my timeline for an greater Macedonian empire.
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325 BCE: Alexander the Great?s armies push into India (in OTL, they mutinied before conquering Magadhas). The Macedonian armies conquer to the upper Ganges Plain and the region where Delhi is in the modern day, before monsoons and rival armies from the kingdom of Bihar stop Alexander?s armies. Alexander and his troops stay there for several months, eliminating resistance and consolidating power there. The incredible wealth of India contents the previously unrestful soldiers, and several colonies of Greeks and Persians are settled in a new Alexandria upon the Ganges. During this time, Alexander becomes familiar with Buddhism, and becomes rather fond of it, considering its use as a legitimizing doctrine for the Oiekumene.
324-323 BCE: Alexander and his troops and entourage, now in solid control of Northern India, march back to Babylon. Upon his arrival in the city, Alexander proclaims the city his new capital, and begins planning the structure of his Oiekumene, restructuring the Persian civil service bureaucracy, integrating Greek culture with that of the Near East, and planning the his next conquest: Arabia Felix, the wealthy regions of coastal Arabia. The ports of the Oiekumene begin the construction of a massive fleet of ships to circumnavigate the Arabian Peninsula and conquer it.
322 BCE: The Alexandrian fleets sail to conquer Arabia. Many ships are lost in the shallow coastal waters, but many also make it through. The wealthy coastal regions are quickly taken by Alexander?s troops, but the push into the desert is much harder.
322-310 BCE: After ten years of fighting, Alexander?s armies establish loose control of inner Arabia and total control of Arabia Felix. Alexander, now too exhausted and battered to continue conquering, busies himself with matters of state and drunken binges. Construction on a vast network of roads is begun. A system of weights and measures is introduced and banditry and other outlaws are crushed. Alexander continues, with limited success to integrate Greek and Persian cultures. Alexander vigorously encourages Greek colonization throughout the Oiekumene. Bactria, Persia, Northern India and Egypt all gain a much higher Greek population.
310-302 BCE: Alexander patronizes Buddhism in the Oiekumene, though not converting to it himself. Buddhist monasteries and temples are sponsored in Babylon, Alexandria and Persia. At this time, raiding by nomads on the northern frontiers becomes a serious problem, causing skirmishes in many areas, especially Persia and the Macedonian northern border. Alexander also begins planning his invasion of Carthage, ordering the construction of another massive fleet to conquer the city.
302 BCE: Alexander dies with his son Philip III as heir. Philip is a ruthless and somewhat paranoid individual, and upon his ascension, he immediately executes or exiles Ptolemy, Seleucus and Antigonus and has several rival family members murdered. Philip then resumes his father?s project to invade Carthage. When the Alexandrian fleet arrives at the city, the Carthaginians simply surrender without a fight and accept vassal status.
300 BCE: The Alexandrian Oiekumene becomes involved in a dispute between Romans, Samnites and Greeks in Italy, leading to the Alexandrians annexing Sicily and the Greek colonies in coastal Italy, and ransacking Rome and several other cities.
300-280 BCE: The Alexandrian Oiekumene is now by far the dominant power in Europe and Asia, with incredible wealth and near-limitless manpower. About this time, the road network is completed, allowing a dramatic increase in trade and communication. Buddhism becomes increasingly popular in the ?fringe? areas of the Alexandrian Oiekumene, such as Bactria, India, Syria, Mesopotamia, and Arabia Felix. Buddhists also achieve some slight popularity in Alexandrian Egypt and Greece itself. Zoroastrianism is also becoming more powerful, supplanting the old Aryan pantheon in Persia.