At the time of the death of Bagrat III, outside the unified Georgian Kingdom still remained Tbilisi, which was the centre of a little Mohammedian Princedom, and the Southern part of Georgia, which was conquerred by the Bizantium Empire in 1001. So, the main problem of the inheritors of Bagrat III was to join these territories.
Giorgi I (1014-1027) fighted with Bizantinnes to get back Georgian lands in vain. At the beginning of reign of his son, Bagrat IV (1027-1072) Bizantinnes invaded Georgia themselves but they were defeated. Bagrat IV fighted for liberation of Tbilisi and fortresses, which were still in the hands of Bizantinnes. But he couldn't end his deed because of particularizm of Feudals and invasions of Selchukid-Turks, who invaded Georgia for the first time in 1064.
The invasions of Selchukid-Turks became wider in 1080. Georgia was cruelly ruined by them, and the important part of the population was exterminated and captured. It forced the King Giorgi II (1072-1089) to visit the Great Sultan of Selchukid-Turks, Melik-Shah, and promise to pay the annual tribute. But it didn't stop the raids of the Turkish separate groups in Georgia. Besides there were the garrisons of Selchukid-Turks in the most important fortresses of Eastern Georgia (Tbilisi among them).
The situation was changed at 90s, in the XI c. when after the death of Melik-Shah, in the Kingdom of Selchukid-Turks set anarchy, and from the West part it was advanced by European Crusaders. The new King of Georgia David IV (1089-1125) used this situation well and in 1097 stopped paying the tribute to Selchukid-Turks and began struggles for the final banishment of the enemy from Georgia. David was a vigorous person, was a clever general and the great statesman. The reforms held by him made Georgia become the strong Kingdom. With the leadership of David, Georgians defeated Selchukid-Turkish armies several times and in 1122 advanced Tbilisi which was declared as the Capital of Georgia.
After liberation of Georgian lands in 1123-1124, David IV banished Selchukid-Turks from the neighbouring Armenian and Azerbaijanian provinces and annexed these territories to Georgia. Thus, at the end of the reign of the King David, estate of Georgia was from the Black Sea to the Caspian Sea.
David IV also drew his attention to construction of cities, roads and bridges, which supported the economical revival of Georgia. The King, who was very educated for this period, and fond of books, cared for the development of cultural-educational centres too. For example, at the Gelati Cloister, with his indication, there was created Academy, where the subjects: philosophy, astronomy, mathemathics, rethorics, music and others were taught. The other Academy was established in Ikalto (East Georgia). For such many-sided constructive activity, Georgian people called David IV "David the Builder".
From the period of David the Builder, begins Feudal, so-called "The Golden Age" of Georgia, the most important period of political, cultural and economical blossom. In the periods of Giorgi III (1156-1184) and the King Tamar (1184-1213) Georgia was one of the strongest Kingdoms in Near East. The wars mostly ended with the victory of Georgian Armies. With the scale and political results, the struggles of Shamkor (1195) and Basiani (1203) are especially important, where Georgians defeated forces of Governors of North-West Iran and Small Asia. In the period of the King Tamar the Kingdom of Georgia owned the big part of Transcaucasus and its political influence was spread on the neighbouring territories - from the North Caucasus Highland till the Southern Coast of the Black Sea, where in 1204, with the efforts of the King Tamar was established the Greek-Georgian Trabson Empire.
The one of the important factors, which conditioned the success of Georgian armament, was the military activity, perfected in numerous wars. The kernels of the Georgian armed forces were the permament army of the King and the knight-aznaur groups, based on the feudal system, and the kernel of helping force was contingents of allies and hired groups, mainly from the North Caucasus. In the first quarter of the XII-XIII cen. Georgians could lead to the struggle 60-90 thous. warriors at the same time. It was mainly cavalry, which was well armed and recruited.
The military-political strength of Georgia relied on developed many-sided economic. To the economical strength of the country indicates creation of complicated system of irrigating chanells. For example, during the reign of the King Tamar, only one such chanell was 119 km long and watered the area of 53.000 hectares. Besides the chanell-building, there also developed gardening, viticulture ans husbandry. Georgia was famous with flax, rice, cotton and seliculture. The second important part of agriculture was cattle-breeding.
The main centres of trade and handicraft were cities. At the beginning of the XIII c. there lived approximately 100.000 people in Tbilisi. The important cities also were Kutaisi, Rustavi, Gori, Dmanisi and etc.
Georgia was trading with the countries of Near East, Bizantium and Russia.
In the XI-XIII c. Georgian Feudal culture reached the top of blossom. There developed philosophical thinking, histography, philology, ecclesiastical and national literature, art. To the end of the XII c. belongs the works of Georgian great poet - Shota Rustaveli, who's poem, "Knight in the Panther's Skin" is one of the masterpieces of the World Literature.
In the XII cen. there also was created an official collection of Georgian historical esseys "Kartlis Tskhovreba". The chronicles of the authors of the VIII-XII cen. were unified in the collection so that it became the permanent decription of history of Georgia from ancient times till the time of creation of the book. Then, untill the XVIII cen. the "Kartlis Tskhovreba" was periodically completed with new esseys. Thus was established the main written source of history of Georgia of Feudal Age, which included the most important datas also about the other coutries of Caucasus.
Important Georgian Architectural Monuments, which are created in this period are Bagrati, Svetitskhoveli and Alaverdi Cathedrals (XI c.), Gelati Cloister, the King's Palace in Geguti, Cloister in the Rock, Vardzia (XII c.), Phitareti and Betania Churches (the beg. of the XIII c.) and others. In the Churches and Cloisters there still are the brilliant examples of stone carving and mural painting. On the high level of development was also decoration of manuscripts, gold-work, production of partitional enamel and etc.
After the death of the King Tamar on the Throne set her son, Lasha-Giorgi IV (1213-1222). The beginning of his reign was notified with the military successes. Inspired by his victories, Giorgi IV was going to make the Crusade in Palestine, but at the borders of Georgia in 1220 suddenly appeared Mongolians of Genghis Khan. In the struggle against them, the King was wounded and soon died. On the Throne of Georgia set his sister Rusudan (1222-1245).