First Republic of Armenia

The First Republic of Armenia, officially known at the time of its existence as the Republic of Armenia, was an independent Armenian state that existed from May (28th de jure, 30th de facto) 1918 to 2 December 1920 in the Armenian-populated territories of the former Russian Empire known as Eastern or Russian Armenia. The republic was established in May 1918, with its capital in the city of Yerevan, after the dissolution of the short-lived Transcaucasian Federation. It was the first Armenian state since the Middle Ages.

In its first year of independence, Armenia was confined to a small territory around Lake Sevan after its invasion by the Ottoman Empire during the Caucasus campaign. Following the Armistice of Mudros, Armenia expanded its borders in the wake of the Ottoman withdrawal, leading to a brief border war with neighbouring Georgia. During its first winter, hundreds of thousands of refugees in the country who had fled the Armenian genocide died from starvation or exposure. In the spring of 1919, Armenia, with British support, incorporated the formerly occupied regions of Kars and Nakhchivan, thereby tripling in size since independence; however, Armenian control of these regions collapsed during the Muslim uprisings that erupted in the summer of 1919.

In late 1919, the isolated Armenian region of Zangezur came under attack by neighbouring Azerbaijan. The fighting subsided until an Armenian rebellion was launched in March of the following year in Nagorno-Karabakh (then under provisional Azerbaijani rule), ending in April after Azerbaijan's sovietisation. In August 1920, Armenian representatives at the Paris Peace Conference signed the Treaty of Sèvres, which awarded Armenia an additional 40,000 square miles (100,000 square kilometres) of territory in Western Armenia, albeit the treaty was never implemented.