The classical period saw the rise of the early Georgian states; Diauehi, Colcis, Sper, and Iberia, not to be confused with the peninsula in western Europe. In the 4th century BCE, a unified kingdom of Georgia was established, an early example of an advanced state under one king and aristocratic hierarchy. Georgia is also prevalent in Greek mythology; Colchis was the location of the Golden Fleece sought by Jason and the Argonauts in Apollonius Rhodius' epic tale Argonautica. Colchis was also the battlefield of the Lazic War fought between the Byzantines and Persia. After the Roman Empire completed its brief conquest of the Caucasus region in 66 BCE, its rival, the Persian Parthian Empire, took back the region. Despite this, the surrounding Georgian kingdoms were Roman client states and allies for over 400 years. In 337 AD King Mirian III declared Christianity as the state religion, giving a great stimulus to the development of literature, arts, and ultimately playing a key role in the formation of the unified Georgian nation. Mirian's acceptance of Christianity tied it to its nearby neighbor, the Eastern Roman Empire, determining much of its present cultural identity. The early kingdoms disintegrated into various feudal regions by the early Middle Ages, making it east for Arabs to conquer eastern Georgia from the 7th-10th centuries BCE, Georgia was part of the Khazar Empire. The various independent regions would not be united into a single Kingdom of Georgia until the beginning of the 11th century. Although Arabs captured the capital city of Tbilisi in 645 AD, Georgia was semi-independent under local Arab rulers. The prince Ashot I (r. 813–830) – also known as Ashot Kurapalat – became the first of the Bagrationi family to rule the kingdom. Ashot's reign began a period of nearly 1,000 years during which the Bagrationi, as the noble house was known, ruled parts of the modern Georgian states. The 29-year reign of Tamar, the first female ruler of Georgia, is considered the most successful in Georgian history. She was given the title "king of kings", and neutralized opposition and embarked on an energetic foreign policy aided by the downfall of rival Selijuks and Byzantium. She was able to solidify Georgia's place as a regional power; this empire lasted until its conquest by the Mongolia. The revival of the Kingdom of Georgia was set back after Tbilisi was captured and destroyed by the Khwarezmian leader Jalal ad-Din in 1226. The Mongols were pushed back by George V, son of Demetrius II of Georgia, who had brought back his country's previous strength. George V was the last great king of the unified Georgian state. After his death, different local rulers fought for their independence from central Georgian rule, until the total disintegration of the Kingdom in the 15th century. Afterwards, Iran and the Ottoman Empire would divide Georgia. The regions remained somewhat autonomous and organized revolutions on numerous occasions, however subsequent Persian and the Ottoman invasions would further weaken the region. With the death of Nader Shah in 1747, both kingdoms broke free of Iranian control and were reunified through a personal union under the energetic king Heraclius (Erekle) II in 1762. He stabilized Georgia to a degree and gave it autonomy from the Russian Empire (Franco-American War)Persian Zand period.
In 1783, Russia and Georgia signed a treaty recognizing the religious bond between the Russian and Georgian people, and promised Georgia protection against any potential Iranian attempts to regain the country. However, despite this treaty, the Russians didn't help when Iran invaded, sacking Tbilisi. On December 22, 1800, Tsar Paul I of Russia and George XII signed the proclamation of Georgia's incorporation into the Russian Empire, which was finalized on September 12, 1801. In the summer of 1805, Russian troops defeated the Iranian army during the Russo-Persian War, which lasted until 1813. Russian sovereignty over Georgia was confirmed with the end of this war. Following the annexation of eastern Georgia, the western Georgian kingdom of Imereti was annexed by Tsar Alexander I. Thanks to several wars against the Ottoman Empire, Russia was able to gain much of Georgia's western territories, absorbing Adjara, Guria, Mingrelia, and Svaneti into the empire. During the Russian Civil War, Georgia declared its independence from the falling Russian Empire, creating the modern-day republic