The Golden age of Georgia left a legacy of great cathedrals, romantic poetry and literature, and the epic poem "The Knight in the Panther's Skin". David the Builder is popularly considered to be the greatest and most successful Georgian ruler in history. He succeeded in driving the Seljuks out of the country, winning the major Battle of Didgori in 1121. His reforms of the army and administration enabled him to reunite the country and bring most Caucasian lands under Georgia’s control. >>>>>
David the Builder's granddaughter Tamar was successful in neutralizing this opposition and embarked on an energetic foreign policy aided by the downfall of the rival powers of the Seljuks and Byzantium. Supported by a powerful military élite, Tamar was able to build on the successes of her predecessors to consolidate an empire which dominated the Caucasus until its collapse under the Mongol attacks within two decades after Tamar's death.
The revival of the Georgian Kingdom was short-lived; in 1226 Tblisi was captured by Mingburnu and the Kingdom was eventually subjugated by the Mongols in 1236 (see Mongol invasions of Georgia). Thereafter, different local rulers fought for their independence from central Georgian rule, until the total disintegration of the Kingdom in the 15th century. Georgia was subjected, between 1386 and 1404, to several disastrous invasions by Tamerlane. Neighbouring kingdoms exploited the situation, and beginning in the 16th century, the Persian Empire and the Ottoman Empire subjugated the eastern and western regions of Georgia, respectively.
The rulers of regions which remained partly autonomous organized rebellions on various occasions. However, subsequent Persian and Ottoman invasions further weakened local kingdoms and regions. As a result of wars the population of Georgia was reduced to 250,000 inhabitants at one point. Eastern Georgia, composed of the kingdoms of Kartli and Kakheti, had been under Persian suzerainty since 1555. With the death of Nader Shah "The Persian Napoleon" in 1747, both kingdoms broke free of Persian control and were reunified through a personal union under the energetic king Heraclius II in 1762.