The area that is now Nakhchivan became part of Safavid Iran in the 16th century. In 1828, after the last Russo-Persian War and the Treaty of Turkmenchay, the Nakhchivan Khanate passed from Iranian into Imperial Russian possession. After the 1917 February Revolution, Nakhchivan and its surrounding region were under the authority of the Special Transcaucasian Committee of the Russian Provisional Government and subsequently of the short-lived Transcaucasian Democratic Federative Republic. When the TDFR was dissolved in May 1918, Nakhchivan, Nagorno-Karabakh, Zangezur (today the Armenian province of Syunik), and Qazakh were heavily contested between the newly formed and short-lived states of the First Republic of Armenia and the Azerbaijan Democratic Republic (ADR). In June 1918, the region came under Ottoman occupation. Under the terms of the Armistice of Mudros, the Ottomans agreed to pull their troops out of the Transcaucasus to make way for British occupation at the close of the First World War. In July 1920, the Bolsheviks occupied the region and on July 28, declared the Nakhchivan Autonomous Soviet Socialist Republic with "close ties" to the Azerbaijan SSR, beginning seventy years of Soviet rule. In January 1990 Nakhchivan declared independence from the USSR to protest against the suppression of the national movement in Azerbaijan and became the Nakhchivan Autonomous Republic within the newly independent Republic of Azerbaijan a year later.