The Neo-Assyrian Empire dominates the Near East in the early centuries of the millennium, supplanted by the Achaemenid Empire in the 6th century.
Ancient Egypt is in decline, and falls to the Achaemenids in 525 BC.
In Greece, Classical Antiquity begins with the colonization of Magna Graecia and peaks with the conquest of the Achaemenids and the subsequent flourishing of Hellenistic civilization (4th to 2nd centuries).
The Roman Republic supplants the Etruscans and then the Carthaginians (5th to 3rd centuries). The close of the millennium sees the rise of the Roman Empire. The early Celts dominate Central Europe while Northern Europe is in the Pre-Roman Iron Age.
In East Africa, the Nubian Empire and Aksum arise.
In South Asia, the Vedic civilization blends into the Maurya Empire. The Scythians dominate Central Asia. In China, the Spring and Autumn period sees the rise of Confucianism. Towards the close of the millennium, the Han Dynasty extends Chinese power towards Central Asia, where it borders on Indo-Greek and Iranian states. Japan is in the Yayoi period. The Maya civilization rises in Mesoamerica.
The first millennium BC is the formative period of the classical world religions, with the development of early Judaism and Zoroastrianism in the Near East, and Vedic religion and Vedanta, Jainism and Buddhism in India. Early literature develops in Greek, Latin, Hebrew, Sanskrit , Tamil and Chinese. The term Axial Age, coined by Karl Jaspers, is intended to express the crucial importance of the period of c. the 8th to 2nd centuries BC in world history.
World population more than doubled over the course of the millennium,
from about an estimated 50–100 million to an estimated 170–300 million.
Close to 90% of world population at the end of the first millennium BC lived in the Iron Age civilizations of the Old World (Roman Empire, Parthian Empire, Graeco-Indo-Scythian and Hindu kingdoms, Han China).
The population of the Americas was below 20 million, concentrated in Mesoamerica (Epi-Olmec culture);
that of Sub-Saharan Africa was likely below 10 million. The population of Oceania was likely less than one million people.