Unification of the Georgian realm

The unification of the Georgian realm (ქართული სახელმწიფოს გაერთიანება) was the 10th-century political movement that resulted in the consolidation of various Georgian crowns into a single realm with centralized government in 1008, the Kingdom of Georgia, or Sakartvelo. It was originally initiated by the powerful local aristocracy of the eristavs, due to centuries-long power struggles and aggressive wars of succession between the Georgian monarchs, arising from their independent ruling traditions of classical antiquity and their Hellenistic-era monarchical establishments in Colchis and Iberia.

The initiative was supported by David III the Great of the Bagrationi dynasty, the most powerful ruler in the Caucasus at the time, who would put prince royal Bagrat, his kin and foster-son, on the Iberian throne, who would eventually be crowned King of all-Georgia. David's Bagratid successors would become the champions of national unification, just like the Rurikids or the Capetians, but despite their enthusiasm, some of the Georgian polities that had been targeted for unification did not join the unification freely and would actively fight against it throughout this process, mostly seeking help and support from the Byzantine Empire and the Abbasid Caliphate. Even though the 1008 unification of the realm would unite most of western and central Georgian lands, the process would continue to the east, and eventually reach its total completion under King David IV the Builder. This unprecedented political unification of lands and the meteoric rise of Bagrationi power would inaugurate the Georgian Golden Age and creation of the only medieval pan-Caucasian empire, attaining its greatest geographical extent and dominating the entire Caucasus in the 11th, 12th and 13th centuries.

The centralizing power of the crown started to weaken in the 14th century, and even though the tide turned back under King George V the Brilliant, the reunification turned out to be short-lived; the unified realm would evaporate after invasions by the Mongols and Timur that would result in its total collapse in the 15th century.

Background
The Sasanian Empire abolished the Georgian monarchy and annexed the Kingdom of Iberia in 580, making it a Sasanian province ruled by the Persian marzbans and later, demoted in rank, by native Iberian princes. In the 8th century Arabs would invade Georgian lands and establish Emirate of Tbilisi, while Georgian dynastic princes would flee to Uplistsikhe and Kakheti. In 888, Adarnase IV would restore the Georgian kingship in the name of the Kingdom of the Iberians, a monarchy that was concentrated on the historical lands of Tao and Klarjeti. The Kingdom of the Abkhazians would be experiencing the dynastic succession crisis, while warmongering and emerging east Georgian power of Principality of Kakheti would be in constant conflict with the Iberian neighbors. At the same time, the Georgian Orthodoxy was expanding and reaching the most eastern regions by 950, when Queen Dinar of Hereti renounced monophysitism, thus making all Georgian polities unified ecclesiastically, making political union inevitable. This was the very time when the concept and a compelling definition of Georgia was introduced by the writer and ecclesiastical lawyer Giorgi Merchule in 951 in his "Vita of Gregory of Khandzta". ქართლად ფრიადი ქუეყანაჲ აღირაცხების, რომელსაცა შინა ქართულითა ენითა ჟამი შეიწირვის და ლოცვაჲ ყოველი აღესრულების. We can consider as Greater Georgia wherever mass and prayers are said in Georgian [language].

Giorgi Merchule advanced the definition of the nation based upon religious and linguistic considerations. This trend would also continue under Georgian Sabaite monk John Zosimus who would attribute divine, unique and sacred role to the Georgian language, that, as he believed, would be a tongue to be used on the Last Judgment. The Georgian liturgical language was a national unifier when political and cultural unity was still very elusive. Eventually, with an immense ideological support from the clerics, the Georgian unification would come from a resurgent Bagrationi family based in the Kingdom of the Iberians and King George II of Abkhazia, and his policy of unifying Georgian polities by interdynastic marriages and intrigues, resulting, his daughter, princess Gurandukht marrying Gurgen, King of Kings of the Iberians, bearing Bagrat, the first all-Georgian king.

Initiative and David III
Georgian monarchies continued being torn apart by their local rulers and rival states. Right after yet another attack by the Principality of Kakheti on Iberian citadel of Uplistsikhe, part of the aristocracy led by one the most powerful and instrumental Georgian feudal lords, the eristavi, Ivane Marushisdze,  who envisaged a unified Georgia with centralized monarchy, addressed and urged childless David III to end the chaos by taking control of all central Georgian lands and its core region of Kartli and to put his kin, prince Bagrat on throne, thus laying future foundation for a unification process of various lands into a single crown. If David III were to designate Bagrat his heir, Marushisdze reasoned, the extensive realm of David would be merged with lands of Bagrat, thus creating a formidable all-Georgian enterprise.

მაშინ მოვიდეს კახნი და მოადგეს უფლისციხესა. და იყო მათ ჟამთა ერისთავი, ქართლისა ივანე მარუშისძე, კაცი ძლიერი და ერმრავალი. ამან წარავლინა მოციქული წინაშე დავით კურაპალატისა; აწჳა, რათა გამოილაშქროს ძალითა მისითა, აღიღოს ქართლი: ანუ დაიმჭიროს თჳთ, ანუ უბოძოს ბაგრატს, ძესა გურგენისსა, ასულისწულსა გიორგი აფხაზთა მეფისასა, რომელსა ეყოდა დედულად აფხაზეთი და ქართლი. ესევე ივანე მარუშისძე ეძებდა ბაგრატს მეფედ. And then the Kakhetians invaded, and approached Uplistsikhe. And there was eristavi of Kartli, Ivane Marushisdze, a man of strength and with abundance of warriors. He sent an apostle to David [III] kouropalates; he told him to invade and conquer Kartli with his strength, and take it; hold it, and give it to Bagrat, son of Gurgen, son of a daughter of George [II], King of the Abkhazians, who should own Abkhazia and Kartli. Ivane Marushisdze saw Bagrat as a King.

The bet of aristocracy on David III was no surprise as he was the major power in Caucasian and Byzantine commonwealth. David rose from an obscure non-royal branch of the Bagrationi family to glory thanks to his military valor and skills. David's armies would rescue the Byzantine emperor Basil II the Bulgar Slayer and the empire's Anatolian possessions from the rebel Bardas Skleros. David, with another Georgian, the hiero-strategos ("monk-warrior") John Tornike would lead 12,000 Georgian cavalrymen with Byzantine and Armenian soldiers at the Battle of Pankaleia defeating the emperor's rebels. Basil II would later reward David with a life-long, if not hereditary, grant of the vast lands in the south-eastern Anatolia. His unique position was the perfect pretext for the Georgian aristocracy to push David for unification. David accepted the aristocratic call. In 975 David adopted prince Bagrat and invaded Kartli. David took young Bagrat, his biological parents Gurgen and Gurandukht, to Uplistsikhe, then besieged by Kakhetian forces. The Kakhetians realized that all western and southern Georgia had now united against them. They had to accept David’s presentation of Bagrat as his "heir".

შემოკრიბნა ქართველნი აზნაურნი და უბრძანა. ესე არს მკჳდრი ტაოსი, ქართლისა და აფხაზეთისა, შვილი და გაზრდილი ჩემი, და მე ვარ მოურავი ამისი და თანაშემწე; ამას დაემორჩილენით ყოველნი. და დაყვნა დღენი მცირედნი და წარვიდა ტაოს. He [David] gathered all Georgian aznauris and ordered. He [Bagrat] is an heir of Tao, Kartli and Abkhazia, my son whom I brought up, I am his governor and helper; all of you will obey him. And he [David] stayed there couple of days, and left for Tao.

David acted decisively to ensure Bagrat also inherited the Abkhazian throne. By his mother Gurandukht, young Bagrat was nephew and heir to the blind and childless king Theodosius III of Abkhazia. A little later that same year, in 975, three years prior Theodosius III even died, David invited King Smbat II of Armenia to accompany him, Bagrat and Gurandukht to Kutaisi, where Bagrat was solemnly anointed king of Abkhazia, as Bagrat II.

იწყო განგებად და საურავად და განმართებად ყოველსა საქმესა მსგავსად პაპისა მისისა, დიდისა გიორგი მეფისა, გინა თუ უმეტესადრე ვთქუა, რამეთუ ყოვლითურთ მიემსგავსებოდა ქცევასა გამზრდელისა თჳსისასა, დიდისა მეფისა დავით კურაპალატისასა. He [Bagrat] started to rule per all the deeds of his grandfather, Great King George [II of Abkhazia], to say more, he was much alike of the behavior of his foster-father, Great King David [III] kouropalates.

Unified realm
David III was ruthless and followed aggressive expansion of his realm. The conspirators poisoned his communion wine on the eve of Good Friday, in 1000 or 1001. Whoever hired the murderers, emperor Basil II, or even resentful Georgian nobles, the legacy of David's unification process in the history of Georgian statehood was enormous. Prince Bagrat was made King of Abkhazia officially in 978. When his father, Gurgen, died in 1008, Bagrat’s claim to the Abkhazian and Iberian thrones, was undisputed. He became the first ruler of all-Georgian monarchy, as King Bagrat III, and officially styled as the "King of the Abkhazians and Iberians". It was only a matter of time before monarchies of Kakheti and Hereti also submitted to his unified Georgian realm, while the emirate of Tbilisi lingered on.

და შემდგომად ამისა რაოდენთამე წელთა გარდაიცვალა ესე გურგენ მეფეთ-მეფე, მამა ამის ბაგრატ მეფისა და ძე ბაგრატ მეფე რეგუნისა. მოიწყუნა და განაგნა ყოველნი საქმენი აფხაზეთისანი. ურჩნი თჳსნი შეცვალნა დიდებისაგან და ადგილთა მათთა დაადგინნა ერთგულნი და მოსწრაფედ მორჩილნი ბრძანებათა მისთა. და წარემატა ყოველთა მეფეთა აფხაზეთისა და ქართლისათა ყოვლითა განგებითა. და განამრავლა ლაშქარი თჳსი უმეტეს ყოვლისა ჟამისა. ბაგრატ მეფემან კურაპალატმან დაიპყრა ყოველი კავკასია თჳთმპყრობელობითა ჯიქეთითგან ვიდრე გურგენადმდე, და ადარბადაგანი და შირვანი მოხარკე ყო სომხითისა ჴელმწიფებითა. მეფე სპარსთა მეგობარ და ერთგულ ყო სიბრძნითა და ძლიერებითა თჳსითა, უფროს სახლეულთა თჳსთასა, და ბერძენთა მეფესაცა შიში აქუნდა ამისი ყოვლადვე. And later in couple of years died King of Kings Gurgen, father of King Bagrat, and son of King Bagrat [II] Regueni. He organized all the matters of Abkhazia. He changed the rebellious nobles and put in place loyal and fast doing servants of his orders. And he succeeded all the deeds of the kings of Abkhazia and Kartli. And multiplied he his army of all times. King Bagrat the kouropalates conquered all the Caucasus with his sovereignty, from Jiketi to Gorgan, and made Adurbadagan and Shirvan as his tributaries through sovereign rule over Somkhiti. He [Bagrat], with his wisdom and strength, made the King of the Persians as his loyal friend, and the King of the Greeks was greatly afraid of him [Bagrat] too.

Bagrat III, being precociously far-sighted and ruthless, would continue the expansion of his unified realm and the suppression of the rebellious separatist aristocracy, including purging his own cousins so no rival Bagrationi could ever claim the Georgian throne.