The Jewish diaspora (or simply the Diaspora; Hebrew Galut גלות; Yiddish Golus) was the historical exile of Jews from the region of the Kingdom of Judah and Roman Judaea, as well as the later emigration from wider Eretz Israel.
The diaspora began with the 6th century BCE conquest of the ancient Kingdom of Judah by Babylon, the destruction of the First Temple (c. 586 BCE), and the expulsion of the population, as recorded in the Bible. The Babylonian ruler, Nebuchadnezzar, allowed the Jews to remain in a unified community in Babylon. Another group of Jews fled to Egypt, where they settled in the Nile delta. From 597 BCE onwards, there were three distinct groups of Hebrews: a group in Babylon and other parts of the Middle East, a group in Judaea, and another group in Egypt. While Cyrus the Persian allowed the Jews to return to their homeland in 538 BCE, most chose to remain in Babylon. A large number of Jews in Egypt became mercenaries in Upper Egypt on an island called the Elephantine. Most of these Jews retained their religion, identity, and social customs; both under the Persians and the Greeks, they were allowed to conduct their lives according to their own laws.
In 63 BCE, Judaea became a protectorate of Rome, and in 6 CE was elevated to a Roman province. The Jews began to revolt against the Roman Empire in 66 CE during the period known as the First Jewish–Roman War which culminated in the destruction of Jerusalem in 70 CE. During the siege, the Romans destroyed the Second Temple and most of Jerusalem. In 132, the Jews rebelled against Hadrian. In 135, Hadrian’s army defeated the Jewish armies and Jewish independence was lost. Jerusalem was turned into a pagan city called Aelia Capitolina and the Jews were forbidden to live there, and Hadrian changed the country’s name from Judea to Syria Palestina.
During the Middle Ages, the Jews had divided into distinct regional groups which today are generally addressed according to three primary geographical groupings: the Ashkenazi Jews who settled in Northern and Eastern Europe, the Sephardi Jews who settled in Iberia and later North Africa, and the Mizrahi Jews who remained in the Babylon after the destruction of the First Temple. Ashkenazi populations grew rapidly from the 16th to the 19th centuries, with the largest diaspora populations in the Polish–Lithuanian Commonwealth and the Russian Empire. Millions of Jews migrated to the Americas in the 20th century. In the early 21st century the largest diaspora populations were in the United States (~ 5.75 million), France (~ 475,000), Canada (~ 375,000), the United Kingdom (~300,000), Russia (~ 200,000), Argentina (~200,000) and Germany (~120,000).
Read more about Galut: Origins of The Term, Pre-Roman Diaspora, Roman Destruction of Judea, Dispersion of The Jews in The Roman Empire, Post-Roman Period Jewish Populations, The "Negation of The Diaspora" By Zionism, Mystical Explanation, The Diaspora in Contemporary Jewish Life