During the 19th the Caucasus region was contested between the declining
Ottoman Empire,
Persia and
Russia, which was expanding southwards. Russia had conquered most of Persia's Caucasian lands by 1828 and then turned its attention to the Ottoman Empire. By the 1829
Treaty of Adrianople (ending the
Russo-Turkish War of 1828–29) Russia gained most of modern Georgia (including
Imeretia,
Mingrelia and
Guria), with a frontier being delimited situated roughly north of the current Georgia-Turkey boundary. By the
Treaty of San Stefano, ending the
Russo-Turkish War (1877–1878), Russia gained further land in what is now eastern Turkey, extending the Ottoman-Russian frontier south-westwards. Russia's gains of
Batumi,
Kars and
Ardahan were confirmed by the
Treaty of Berlin (1878), though it was compelled to hand back part of the area around Bayazid (modern
Doğubayazıt) and the
Eleşkirt valley. During the
First World War Russia
invaded the eastern areas of the Ottoman Empire. In the chaos following the
1917 Russian Revolution the new Communist government hastily sought to end its involvement in the war and signed the
Treaty of Brest-Litovsk in 1918 with Germany and the Ottoman Empire. Internal disagreements led to
Georgia leaving the federation in May 1918, followed shortly thereafter by
Armenia and
Azerbaijan. With the Ottomans having
invaded the Caucasus and quickly gained ground, the three new republics were compelled to sign the
Treaty of Batum on 4 June 1918, by which they recognised the pre-1878 border. Ottoman gains in Armenia were consolidated further by the
Treaty of Aleksandropol (1920). With the Ottoman Empire defeated in Europe and Arabia, the Allied powers planned to partition it via the 1920
Treaty of Sèvres. The treaty recognised Georgian and Armenian independence, granting both vast lands in eastern Turkey, with an extended Armenia-Georgia border to be decided at a later date; Georgia was to gain much of
Lazistan. Turkish nationalists were outraged at the treaty, contributing to the outbreak the
Turkish War of Independence; the Turkish success in this conflict rendered Sèvres obsolete. Georgia was initially incorporated along with Armenia and Azerbaijan in the
Transcaucasian SFSR within the
USSR, before being split off as the
Georgian Soviet Socialist Republic in 1936. The Kars Treaty border remained, despite occasional Soviet protests, notably in 1945, that it should
be amended. Turkey, backed by the US, refused to discuss the matter, and the Soviets, seeking better relations with their southern neighbour, dropped the issue. ==Settlements near the border==