4th century BC

Millennium:	1st millennium BC
Centuries:	5th century BC; 4th century BC; 3rd century BC;
Decades:	390s BC 380s BC 370s BC 360s BC 350s BC; 340s BC 330s BC 320s BC 310s BC 300s BC
Categories:	Births – Deaths; Establishments – Disestablishments

The 4th century BC started the first day of 400 BC and ended the last day of 301 BC. It is considered part of the Classical era, epoch, or historical period.

Map of the world in 323 BC (at the death of Alexander the Great)

This century marked the height of Classical Greek civilization in all of its aspects. By the year 400 Greek philosophy, art, literature and architecture had spread far and wide, with the numerous independent Greek colonies that had sprung up throughout the lands of the eastern Mediterranean.

Arguably the most important series of political events in this period were the conquests of Alexander, bringing about the collapse of the once formidable Persian Empire and spreading Greek culture far into the east. Alexander dreamed of an east/west union, but when his short life ended, his vast empire was plunged into civil war as his generals each carved out their own separate kingdoms. Thus began the Hellenistic age, a period characterized by a more absolute approach to rule, with Greek kings taking on royal trappings and setting up hereditary successions. While a degree of democracy still existed in some of the remaining independent Greek cities, many scholars see this age as marking the end of classical Greece.

In India, the Mauryan Empire was founded in 322 BCE by Chandragupta Maurya, who had overthrown the Nanda Dynasty and rapidly expanded his power westwards across central and western India, taking advantage of the disruptions of local powers in the wake of the withdrawal westward by the armies of Alexander.

China in the 4th century BCE entered an era of constant warfare known as the Warring States period. The period saw the rapid rise of large states (such as Chu) over smaller ones thanks to technological advancement. Though the period has usually been characterized by historians as being excessively violent compared to the Spring and Autumn period it was also punctured by several cultural and social growth through the expansion of several different sects of Confucianism and Taoism.

Inventions, discoveries, introductions

A Han Dynasty Chinese crossbow from the 2nd century BC.

Oldest Brāhmī script dates from this period. Brāhmī is the ancestor of Brahmic scripts, used in much of India and Southeast Asia.
Romans build their first aqueduct.
Chinese use the handheld trigger crossbow for the first time.
The first crossbow, the gastraphetes, is invented at Syracuse. (? pre-421 BC)
Burnt brick first used in Greece.^{[citation needed]}
Donkey-powered mills first used in Greece.^{[citation needed]}
In Greece Aristotles proposes the division of the known sciences.
Torque with lion's-head terminals, from Susa (modern Shush, Iran) was made. It is now in Musée du Louvre, Paris.
Daric, a coin first minted under Darius I of Persia is made. It is now kept in Heberden Coin Room, Ashmolean Museum, Oxford.
Second half of the 4th century BC – Tomb II, so called Tomb of Philip II of Macedon, Vergina, Macedonia is made.
Starting in the year 309 BC, the later Chinese historian Sima Qian (145 BC–90 BC) wrote that the Qin-employed engineer Bi Ling of the newly conquered State of Shu in Sichuan had the shoulder of a mountain cut through, making the 'Separated Hill' that abated the Mo River, and excavated two canals in the plain of Chengdu. The significance of this was phenomenal, as it allowed the new Guanxian irrigation system to populate an area of some 40 by 50 miles (60 × 80 km) with over five million people, still in use today (Needham, Science and Civilization in China, Volume 4, Part 3, 288).
The Chinese astronomer Gan De divides the celestial sphere into 365¼ degrees, and the tropical year into 365¼ days at a time when most astronomers used the Babylon division of the celestial sphere as 360 degrees (Deng, Yinke. [2005] (2005). Chinese Ancient Inventions. ISBN 7-5085-0837-8).