Attention now turned to the Murid War (1830-1859) in which the mountaineers of Dagestan and Chechnya united and held out until 1859. In the western mountains the long Russo-Circassian War continued. It ended in 1864 with the expulsion to Turkey of several hundred thousand Circassians. The Crimean War (1853-1856) changed little. In the Russo-Turkish War (1877–78) Russia gained the province of Kars and the port of Batum. During World War I Russia collapsed during the Revolution and the Turks pushed as far east as Baku but then withdrew when their own empire collapsed. In the post-war confusion, Turkey regained Kars. During World War II the Nazis got a little beyond Maikop but were unable to reach the Baku oil-fields. After the war Russia tried and failed to take part of northern Persia. In 1991 Transcaucasia became independent as the states of Georgia, Armenia and Azerbaijan. In 1992 Abkhazia and South Ossetia became de facto independent of Georgia with Russian backing. In 1994 Nagorno-Karabakh was de facto taken from Azerbaijan by Armenia.