was threatened with collapse until the intervention of the Great Powers in the Battle of Navarino in 1827. The Ottoman fleet was decisively defeated by the combined fleets of the Britain, France and the Russian Empire, effectively securing the independence of Greece. 1850 to the end of the century Most warships used steam propulsion until the advent of the gas turbine. Steamships were superseded by diesel-driven ships in the second half of the 20th century. The Confederate States Navy (CSN) was the naval branch of the Confederate States armed forces established by an act of the Confederate Congress on February 21, 1861. It was responsible for Confederate naval operations during the American Civil War. The two major tasks of the Confederate Navy during the whole of its existence were the protection of Southern harbors and coastlines from outside invasion, and making the war costly for the North by attacking merchant ships and breaking the Union Blockade. David Farragut was the first senior officer of the United States Navy during the American Civil War. He was the first rear admiral, vice admiral, and full admiral of the Navy. He is remembered in popular culture for his possibly apocryphal order at the Battle of Mobile Bay, usually paraphrased: "Damn the torpedoes, full speed ahead!". Franklin Buchanan was an officer in the United States Navy who became an admiral in the Confederate Navy during the American Civil War. He was the captain of the ironclad (formerly ) during the Battle of Hampton Roads in Virginia. He climbed to the top deck of Virginia and began furiously firing toward shore with a carbine as was shelled. He soon was brought down by a sharpshooter's minie ball to the thigh. He would eventually recover from his leg wound. He never did get to command Virginia against . That honor went to Catesby ap Roger Jones. But Buchanan had handed the US Navy the worst defeat it would take until Pearl Harbor. Raphael Semmes was an officer in the United States Navy from 1826 to 1860 and the Confederate States Navy from 1860 to 1865. During the American Civil War he was captain of the famous commerce raider , taking a record fifty-five prizes. Late in the war he was promoted to admiral and also served briefly as a brigadier general in the Confederate States Army. In Italy, Carlo Pellion di Persano was an Italian admiral