High Quality Content by WIKIPEDIA articles! The Alma class ironclads were a group of seven wooden-hulled, armored corvettes built for the French Navy in the mid to late 1860s. Three of the ships attempted to blockade Prussian ports in the Baltic Sea in 1870 during the Franco-Prussian War. Three others patrolled the North Sea and the Atlantic, while the last ship was enroute to Japan when the war began and blockaded two small Prussian ships in a Japanese harbor. Afterwards they alternated periods of reserve and active commissions, many of them abroad. Three of the ships participated in the French occupation of Tunisia in 1881 while another helped to intimidate the Vietnamese Government into accepting status as a French protectorate and played a small role in the Sino-French War of 1884–85.