The Turkish-Armenian war, known in Turkey as the Eastern Operation or Eastern Front  of the Turkish War of Independence, refers to a conflict in the autumn of 1920 between the First Republic of Armenia and the Turkish nationalists, following the signing of the Treaty of Sèvres. After an initial Armenian occupation of what is now eastern Turkey, the army of the Turkish National Movement under Kâzım Karabekir reversed the Armenian gains and further invaded and defeated Armenia, also recapturing territory which the Ottoman Empire had lost to the Russian Empire in 1855 and 1878. The Turkish military victory was followed by Soviet Russia's occupation and sovietization of Armenia. The Treaty of Moscow  between Soviet Russia and the Grand National Assembly of Turkey and the related Treaty of Kars  confirmed the territorial gains made by Karabekir and established the modern Turkish-Armenian border. Armenia had territorial disputes with the Ottoman Empire. The Ottomans had tried to move the Armenians during the Armenian Genocide and occupied the South Caucasus during Summer 1918. Armenia resisted until the Allied forces won WWI. The Ottomans maintained their troops along their territorial gains until Spring 1919.

What happened second: Eastern Operation or Treaty of Moscow?
Eastern Operation