The Russian (Tsarist) army occupied Iranian Azerbaijan in 1909 and again in 1912–1914 and 1915–1918, followed by Ottoman forces in 1914–1915 and 1918–1919; Bolshevik forces occupied Iranian Azerbaijan and other parts of Iran in 1920–1921, [permanent dead link] and Soviet forces occupied Iranian Azerbaijan in 1941, creating a very short-lived autonomous, Soviet-supported …
A bunker is a defensive military fortification designed to protect people and valued materials from falling bombs or other attacks. Bunkers are mostly underground, in contrast to blockhouses which are mostly above ground. They were used extensively in World War I, World War II, and the Cold War for weapons facilities, command and control centers, and storage facilities.