By the end of the 15th century, the Kingdom of Georgia was fragmented into a number of petty client kingdoms subject to either Persia (Kingdom of Kakheti, Kingdom of Kartli) or the Ottomans (Kingdom of Imereti). Throughout the 16th century, the Caucasus continued to serve as a battleground between Persian and Ottoman forces, with the two great powers attempting to gain control over the region. From the 1530s to the 1550s, several Transcaucasian cities became the focal point of these imperial divides. In 1555, this culminated in the Peace of Amasya, whereby Ottoman and Persian forces agreed to establish formal spheres of influence in the region. As a result of the Treaty, the Safavid Empire (Persia) assumed control over lands East of the Surami Highlands, including the Georgian kingdoms of Kartli and Kakheti. The Ottomans received areas West of the Highlands, including the Georgian kingdom of Imereti. The nascent Russian Empire gained territories in the North Caucasus in the &lt;a href="Russo-Persian%20War%20%281722%E2%80%9323%29"&gt;Russo-Persian war of 1722/3&lt;/a&gt;. These territories were ceded back to Persia a few years later. Following the death of Nader Shah, Kartli and Kakheti were merged into the Kingdom of Kartli-Kakheti in 1762; Erekle "de facto" seceded from Persian overlordship, but still "de jure" recognized the Persians as his suzerain. In 1783, King Erekle II concluded the Treaty of Georgievsk with the Russian Empire. Catherine the Great tried to use Georgia as a base of operations against both Iran and the Ottoman Empire. After her death, the Russians withdrew to the North Caucasus Line. The Qajar dynasty re-established Persia's traditional suzerainty over the Caucasus. A Persian invasion force defeated the Georgian army in the Battle of Krtsanisi in 1795. In 1801, a few years after the assassination of Agha Mohammad Khan, capitalizing on the eruption of instability in Iran, the Russians annexed eastern Georgia (Kartli-Kakheti).