in 1715, Alexander III of Georgia passed away after a long sickness. He declared his oldest son, Constantine, as an heir to the throne shortly before dying. He also granted Kakheti to his youngest son Leon as an estate. Leon wasn't satisfied with only Kakheti and began preparing for a war with his brother.
First Period (1716-1720)
Constantine was on a hunt outside of Tbilisi when he was informed that his brother was approaching Tbilisi with a large army. Constantine didn't have enough time to organize a counterattack and so he retreated to Imereti. Leon proclaimed himself King of Kartli and Kakheti, he then attempted to invade Imereti to finally depose his brother but his couldn't make his way through the dense forests of Western Georgia. Meanwhile, Constantine requested help from Mamuka II of Circassia but received no reply at all, he made multiple raids into Leon's lands but they were inconclusive.
Second Period (1720-1728)
Gagik Hasan-Jalalyan was the Melik of Karabagh at the time of this conflict. Though he remained neutral during the first faze of war he still had some ambitious ideas. He believed that he was the rightful king of Armenia since House of Hasan-Jalal descended from Arscasid Dynasty of Armenia. he asked for support from Maraghehi Dynasty that gained power after the fall of Safavids. in 1720 'Abbas Maraghehi Invaded Shirvan and Shaki, followed by Gagik's revolt in 1721. in 1722, 'Abbas and Gagik defeated Leon near Lake Sevan and laid siege to Yerevan. City Garrison offered fierce resistance but it eventually fell in 1724. Gagik was proclaimed king of Armenia in ruins of Yerevan that same year. Ottomans saw the opportunity to return lost lands from Georgia and prepared an expedition. A large army Marched into Samtskhe in 1725 and annexed Lazistan before moving further north. Constantin met his foes in an open field despite difference in army size. Georgian Aggressiveness played a huge role in this battle as fierce Georgian Charge broke Turkish Morale and forced them to flee. Constantine wanted to pursue the Turkish Army but invasion from his brother prevented him from doing so. He was forced to sign peace treaty recognizing the territorial losses, planning to regain them afterward. After an Inconclusive battle Leon retreated back to his estate, he was becoming increasingly unpopular with his nobles. In 1726 'Abbas was forced to return to his homeland after multiple revolts erupted around Persia. Gagik proceeded to besiege Kars and Ani. He took Kars but failed to take Ani and retreated back to Yerevan. Leon assumed that tired Armenian soldiers would be easy to defeat so he decided to ambush Gagik and His forces. Battle took place outside of Yerevan and Leon was defeated again. Leon retreated to Tbilisi while Gagik attempted to capture him. Failing to capture leon, Gagik made his way back to Yerevan and pillaged everything on his way. King of Armenia took many castles from 1726 and 1727 and began preparing to take Tbilisi. In 1728, Gagik marched toward Tbilisi. Displeased Kartlian and Kakhetian nobles assassinated Leon and Begged Constantine to help them defend Tbilisi. Constantine had already assembled a big army so he quickly advanced to Tbilisi. Constantine entrenched his Army outside of Castle wall and prepared for the battle. The battle lasted for five days and on the fifth day Gagik was killed by cannon fire. His army attempted to retreat but was routed by Georgian cavalry and destroyed. Upon hearing this, 'Abbas marched to Yerevan and managed to stop Georgian advance but failed to recover lost territories. Ashot, the son of Gagik, was crowned as King of Armenia but he was a puppet of 'Abbas and exercised no real power.
Third Period (1728-1732)
'Abbas attacked Lore multiple times but he's attempts at reconquering lost castles failed utterly. By 1729 Georgian had the upper hand, they invaded Shaki-Shamakhi and were about to launch an attack into Shirvan. 'Abbas rushed to defend Shirvan but there was no invasion, it was a distraction and by the time 'Abbas realized that Yerevan had fallen to Georgians. Georgians proceeded to launch a mass-assault against Maraghehids and made their way to Gilan. At this point 'Abbas was unwilling to continue because that was due to constant encroachments from other Persian states and offered peace.
Peace Treaty and Aftermath
'Abbas agreed to return all conquered lands and pay reparations, in return, King Constantine offered him alliance against Ottomans to which 'Abbas accepted. Constantine removed Mamuka II as the prince of Circassia in favor of his son Archil Bagration-Adigheli. Constantine also participated in Giorgi Dzhokhar's subjugation of Caucasian tribes and helped him against Russian encroachment. Economy began to Increase once again, and Georgia attracted attention of Various European nations. 25 years of peace ensued before Georgia joined the Russo-Turkish war and reconquered majority of lost lands. Georgia became a serious regional power, gaining interest of multiple European Powers, Georgia remained neutral toward Russia. Peace lasted until 1820s.