In 780, Abkhazia, which had escaped the Arab invasions, had emancipated itself from Byzantine suzerainty and established itself as a powerful kingdom and master of the region; in 916, the Abkhazian state reached its apogee by invading Iberia and threatening Armenia.

Exploiting the situation, Kvirike II of Kakheti, who reigned in eastern Georgia, organised raids against Iberia, challenging the power of the Abkhaz monarch.

[4] However, the eristavi (governor) of Kartli, Ioane Marushisdze rebelled against Kvirike II and sought the help of the young Bagrat's adoptive father, David III of Tao.

On hearing the news, David III launched an expedition against the Kakhetians who, after negotiations, returned Kartli to the royal family,[1] but retained the fortresses of Gruvi and Tsirkvali.

Taking advantage of the situation, Ioane Marushisdze, who had already placed Bagrat on the Kartlian throne, tried to bring his protégé to the head of the Kingdom of Abkhazia.

[1] Having become King of Abkhazia, Bagrat III had to return urgently to Kartli, where his mother, the regent Gurandukht, reigned and wanted to make herself independent.

The nobles of Kartli, who appreciated their situation under the regent's reign, refused to recognise Bagrat III as King of Iberia and placed a certain Kavtar Tbeli at their head.

He soon came into possession of the fortress of Ateni and all Kartli south of the Mtkuari, Trialeti, Manglis-khevi, and Skvireti,[8] and then refused to submit to Bagrat III.

The Byzantine emperor Basil II, to whom David had bequeathed the Tao as a result of his role in the Bardas Phokas revolt, decided to force his way back.

As a result, Bagrat III, in addition to his title of King of Abkhazia, became Kuropalates of Iberia, unifying western Georgia in the process, but losing a large part of his family heritage.

In 1008, he received the hereditary title of "King of the Georgians" and the unified duchy of Lower Tao-Javakheti when his father, Gurgen I of Iberia, died.

He appointed a certain Aboulal as mtavari ("count") of the region, but he was overthrown by the local nobility, who took control of the country and decided to unite with Kakheti.

In a short space of time, he completed the annexation of Hereti, domesticated the local nobility in Imereti, and placed the relics of the country's first Orthodox queen near these nobles.

He left the fortress of Bodchorma to Prince Kvirike III of Kakheti, son of Bishop David, but took it from him and annexed the country completely some time later.

[14] Fadl, who had sworn to the death of all Christians and had never met a ruler who could defeat him up to that point, was surprised when he learned of the advance of the armies of two countries that worshipped the Cross, and took refuge in a fortress where he prepared for a difficult siege.

[15] Bagrat took advantage of the situation to seize the lands of Arran, which he made a Georgian province, and began the siege of Shamkor, the fortified town in which the Shaddadid emir had taken refuge.

Georgia's first monarch was also responsible for Bagrati Cathedral, in his capital of Kutaisi,[16] a remarkable religious building, the construction of which was completed in 1003.

The monument was part of UNESCO'S World Heritage from the 18th session in 1994 until 2017, when it was withdrawn because it was "the subject of a major reconstruction project affecting its integrity and authenticity”.

[21] According to Vakhushti Bagrationi and Marie-Félicité Brosset, Emperor Basil II, who did not have such good relations with Georgia, offered the Caucasian Patriarchate the monastery of Kestoria (probably in Greece).

At the same time, the Catholicos-Patriarch of All Georgia acquired no less than one hundred and five villages, silver and gold, icons and crosses to decorate the churches.

[20] According to Vakhushti, writing in the 18th century, it was under Bagrat III's protection that the Svetitskhoveli Cathedral (Mtskheta), now the seat of the Catholicos-Patriarch of Georgia, was built, or rather restored, using the ornaments brought back from Kestoria.