Russian Armenia cause Russo-Persian War of 1826–28
The Russian annexation and Persia's ceding
A turning-point came in 1801 when the Russians annexed the Georgian Kingdom of Kartli-Kakheti, giving them a foothold in Transcaucasia. Over the next three decades, Russia sought to further expand its territory in the Caucasus at the expense of Ottoman Turkey and Qajar Iran. The Russian campaigns found enthusiastic support amongst the Armenians, led by the Bishop of Tbilisi, Nerses Ashtaraketsi, who took part in the fighting in person. The Russo-Persian War of 1804–1813 saw the Russians conquer a bit of territory in eastern Armenia only to renounce most of it at the Treaty of Gulistan.
In 1826, in violation of the Gulistan treaty, the Russians occupied parts of Iran's Erivan Khanate. This sparked the final bout of hostilities between the two; the Russo-Persian War of 1826–1828. In the subsequent war that raged, (Russo-Persian War (1826–1828)), the Qajarid Iranians suffered an even bigger disaster, as Russia occupied as far as Tabriz in  mainland Iran. At the end of the war, in 1828, with the Treaty of Turkmenchay, Iran was forced to cede its territories comprising the Erivan Khanate (comprising modern-day Armenia), the Nakhichevan Khanate, as well as the remainder of the Republic of Azerbaijan that had not been ceded forcefully in 1813. By this time, in 1828, the century-long Iranian rule over Eastern Armenia had thus officially come to an end.