Erekle was able, after centuries of Iranian suzerainty over Georgia, to guarantee the autonomy over his kingdom throughout the chaos that had erupted following Nader Shah's death. He became the new Georgian king of a politically united eastern Georgia for the first time in three centuries. Though Erekle tendered his de jure submission to the newly established Zand dynasty quickly after the unification in 1762, the kingdom remained de facto autonomous for the next three decades to come. In 1783, Erekle signed the Treaty of Georgievsk with the Russian Empire, by which he formally laid Kartli-Kakheti's investiture in the hands of the Russian monarch, and made the kingdom a Russian protectorate. Amongst others, this provided the nominal guarantee for protection against new Iranian attempts, or by any others, to (re)conquer or attack eastern Georgia. By the 1790s, a new strong Iranian dynasty, the Qajar dynasty, had emerged under Agha Mohammad Khan Qajar, which would prove pivotal in the history of the short-lived kingdom.
In the next few years, having secured mainland Iran, the new Iranian king set out to reconquer the Caucasus and to re-impose its traditional suzerainty over the region. After Erekle II refused to denounce the treaty with Russia and to voluntarily reaccept Iran's suzerainty in return for peace and prosperity for his kingdom, Agha Mohammad Khan invaded Kartli-Kakheti, captured and sacked Tbilisi, effectively bringing it back under Iranian control. This was short-lived, however, for Agha Mohammad Khan was assassinated two years later. Erekle II himself died a year after that.
The following years which were spent in muddling and confusion, culminated in 1801 with the official annexation of the kingdom by Alexander I within the Russian Empire during the nominal ascension of Erekle's son Giorgi XII to the Kartli-Kakhetian throne. Following the Russo-Persian War of 1804-1813, Iran officially ceded the kingdom to Russia, marking the start of a Russian-centred chapter in Georgian history.
After Nader Shah's death in 1747, Erekle II and Teimuraz II capitalized on the eruption of chaos in mainland Iran. In the ensuing period Erekle II made alliances with the khans of the area, established a leading position in the southern Caucasus, and requested Russian aid. In 1762, he succeeded his father as king of Kartli, and with already being king of Kakheti, eastern Georgia thus became politically unified for the first time in three centuries. Around 1760, at about the time Erekle II proclaimed the kingdom, it had become evident as well that Karim Khan Zand had become the new dominant Iranian ruler, at least for the time being. In 1762-1763, during Karim Khan's campaigns in Azerbaijan, Erekle II tendered his de jure submission to him and received his investiture as vali ("governor", "viceroy") of Gorjestan (Georgia), the traditional Safavid office, which by this time however had become an "empty honorific". Karim Khan died in 1779 however, with Persia again being engulfed into chaos.
Seeking to remain independent, but also realizing that he would need a foreign protector with regard to his kingdom's foreign policy, King Erekle II concluded the Treaty of Georgievsk with Russia in 1783, resulting in the transfer of responsibility for defense and foreign affairs in the eastern kingdom, as well as importantly, officially abjuring any dependence on Iran or any other power. However, despite these large concessions made to Russia, Erekle II was successful in retaining internal autonomy in his kingdom.