The wealth of the Mawarannahr region is a constant magnet for invasions from the northern steppes and from China.

Numerous intraregional wars are fought between Sogdian states and the other states in Mawarannahr, and the Persians and the Chinese are in perpetual conflict over the region.

Alexander the Great conquers the region in 328 BCE, bringing it briefly under the control of his Macedonian Empire.

In the same centuries, however, the region also is an important center of intellectual life and religion.

Much, if not all, of what is today Tajikistan had been part of the Achaemenid Empire, which Alexander the Great subdues in the fourth century BCE; it now becomes part of the Greco-Bactrian kingdom, one of the successor states to Alexander's empire.

The northern part of what is now Tajikistan is part of Sogdia, a distinct region that intermittently exists as a combination of separate oasis states and sometimes is subject to other states.

The effects of the Greek occupation are noteworthy, even though Alexander's major plans for Mesopotamia go unfulfilled, and his generals do little that is positive for Mesopotamia.

Alexander and his successors build scores of cities in the Middle East that are modeled on the Greek city-states.

One of the most important is Seleucia on the Tigris.

The Hellenization of the area includes the introduction of Western deities, Western art forms, and Western thought.

Business revives in Mesopotamia because one of the Greek trade routes runs through the new cities.

Mesopotamia exports barley, wheat, dates, wool, and bitumen; the city of Seleucia exports spices, gold, precious stones, and ivory.

Cultural interchange between Greek and Mesopotamian scholars is responsible for the saving of many Mesopotamian scientific, especially astronomical, texts.

Nearly all of Babylon opposed the Achaemenids by the fourth century BCE.

Thus, when the Iranian forces stationed in Babylon surrender to Alexander the Great of Macedon in 331 BCE, all of Babylonia hails him as a liberator.

Alexander quickly wins Babylonian favor when, unlike the Achaemenids, he displays respect for such Babylonian traditions as the worship of their chief god, Marduk.

Alexander also proposes ambitious schemes for Babylon.

He plans to establish one of the two seats of his empire here and to make the Euphrates navigable all the way to the Persian Gulf, where he plans to build a great port.

Alexander's grandiose plans, however, never come to fruition.

Returning from an expedition to the Indus River, he dies in Babylon—most probably from malaria contracted there in 323 BCE—at the age of thirty-two.

His generals fight for and divide up his empire in the politically chaotic period after Alexander's death.

Many of the battles among the Greek generals are fought on Babylonian soil.

Greek military campaigns in the latter half of the Greek period are focused on conquering Phoenician ports and Babylonia is thus removed from the sphere of action.

The city of Babylon loses its preeminence as the center of the civilized world when political and economic activity shift to the Mediterranean, where it  is destined to remain for many centuries.

Upper South Asia (333–190 BCE): Imperial Expansion and Cultural Flourishing

Rise and Dominance of the Mauryan Empire

Between 333 and 190 BCE, Upper South Asia witnessed the rise and consolidation of the Mauryan Empire, founded by Chandragupta Maurya around 321 BCE. The empire rapidly expanded under Chandragupta, successfully incorporating vast territories including Magadha, Gandhara, and much of present-day Afghanistan, Balochistan, and northern India. The Mauryan Empire, centered at Pataliputra (modern-day Patna, Bihar), became the first pan-Indian empire, renowned for its centralized administrative system, strong military, and extensive road networks.

Persian and Hellenistic Interactions

Following the decline of the Achaemenid Empire due to Alexander the Great's conquest in 330 BCE, the region experienced significant Greek influence, especially in the northwest. Alexander's brief control of territories including Gandhara and the Indus region introduced Hellenistic cultural elements, which later blended with local traditions, creating a unique Indo-Greek synthesis notably seen in Gandharan art.

Reign and Influence of Emperor Ashoka

The Mauryan Empire reached its zenith under Emperor Ashoka (r. ca. 268–232 BCE), who expanded Mauryan control further into southern regions and parts of present-day Afghanistan. Ashoka's transformative embrace of Buddhism after the bloody Kalinga War had profound implications. Buddhism flourished under Ashoka’s patronage, spreading significantly throughout the region and beyond. Ashoka’s edicts—inscribed on rocks and pillars at strategic locations, such as Laghman (Afghanistan), Mahastan (Bangladesh), and Brahmagiri (Karnataka)—became critical historical sources and symbols of early governance.

Urbanization and Cultural Advancements

This era saw substantial urban growth and cultural advancement, exemplified by cities such as Taxila and Pataliputra, which became renowned centers of education and trade. Economic prosperity facilitated developments in crafts and metallurgy, notably reflected in intricate pottery and widespread use of Northern Black Polished Ware (NBPW).

Integration of Diverse Cultures

The Mauryan administration effectively integrated diverse cultural groups including the Pashtuns and Tajiks in the northwest and indigenous populations across the subcontinent. The continuing eastward movement of Indo-Aryan-speaking peoples and interactions with indigenous Kirāta peoples further diversified cultural practices in the Himalayan foothills, particularly in present-day Nepal, Bhutan, and Sikkim.

Regional Kingdoms and Tribal Confederations

Smaller kingdoms and tribal confederations in the Tarai region (southern Nepal), including the influential Shakya clan of Kapilvastu, continued to thrive economically and culturally, benefiting from interactions with the Mauryan Empire. The Tarai became an important cultural and commercial nexus, integrating local traditions with broader pan-Indian cultural currents.

Philosophical and Religious Developments

Besides Buddhism, Jainism also expanded its philosophical and religious influence, while Zoroastrianism maintained significance, particularly in regions previously influenced by Persian administration. These religious and philosophical currents facilitated broader cultural exchanges, contributing significantly to the region's diversity.

Administrative Innovations

The Mauryan Empire implemented pioneering administrative structures as detailed in the Arthashastra by Kautilya (Chanakya), an influential treatise on governance and economics. The empire established a hierarchical administrative system with provinces and districts managed by centrally appointed officials, enhancing efficiency and control.

Artistic and Architectural Legacy

Artistic expressions reached new heights, marked by the construction of numerous Buddhist stupas, monasteries, and intricate sculptures that combined Hellenistic and indigenous styles. Notable examples include the stupas at Sanchi and artistic relics from Taxila, symbolizing the fusion of diverse cultural influences.

Scientific and Medical Advancements

Advancements in medicine and science flourished during this period. The compilation of significant medical texts like the Charaka Samhita, associated with physician Charaka, provided detailed insights into early Ayurvedic medicine, including concepts of metabolism, digestion, and immunity.

Legacy of the Age

The period from 333 to 190 BCE marked a transformative epoch in Upper South Asia, defined by imperial consolidation, cultural synthesis, and remarkable advancements in governance, arts, and sciences. The Mauryan Empire's expansive influence, Ashoka’s profound religious and ethical reforms, and the integration of diverse cultural traditions laid enduring foundations that significantly shaped subsequent historical trajectories and cultural identities in the region.

Alexander now advances with his army from the Sogdian capital of Maracanda (modern Samarkand) …

…by way of Cyropolis to the Jaxartes (modern Syr Darya), the boundary of the Persian Empire.

Here, he breaks the opposition of the Scythian nomads by his use of catapults and, after defeating them in a battle on the north bank of the river, …

...pursues them into the interior.

On the site of modern Leninabad (Khojent) on the Jaxartes in Sogdiana, Alexander founds a city, Alexandreschate, “Alexandria the Farthest,” not far from the site of Cyropolis, a city of Cyrus II the Great, whom he highly admires. (There is evidence of Achaemenid irrigation at the interesting Bactrian site of Ai Khanum, which cannot definitely be identified as an Alexandria.)

Alexandreschate is a prestige foundation, designed, as explicitly stated by Arrian, for both military and commercial success.

Alexander has already planted a number of new Alexandrias in central Iran, including Alexandria in Areia (Herat), Alexandria in Arachosia, and almost certainly Kandahar (on the exciting evidence of a metrical inscription found there by a British excavation team in 1978).

Outflanked by Alexander, Bessus flees beyond the Oxus (modern Amu Darya).

Alexander, marching west to Bactra-Zariaspa (modern Balkh [Wazirabad] in Afghanistan), appoints loyal satraps in Bactria and Aria.

Crossing the Oxus, he sends Ptolemy in pursuit of Bessus, who has meanwhile been overthrown by the Sogdian Spitamenes.

Bessus is captured, flogged, and sent to Bactra, where he is later mutilated after the Persian manner (losing his nose and ears); in due course, he is publicly executed, by crucifixion, at Ecbatana.

Meanwhile, Alexander threatens to severely punish the Daylamites (an Iranian people of northern Iran) for kidnapping his beloved war-horse Bucephalus, which they promptly return to him.

From Phrada, Alexander and his army …