diesel-electric submarine was the most popular export-sales submarine in the world from the late 1960s into the first years of the 21st century. With a larger 1,000–1,500 tonne displacement, the class was very customizable and has seen service with 14 navies, with 51 examples being built as of 2006. Germany continued to reap successes with derivations or on the basis of the successful type 209, as are the Type 800 sold to Israel and the TR-1700 sold to Argentina. Germany continued to succeed as an exporter of submarines as the Klasse 210 sold to Norway, considered the most silent and maneuverable submarines in the world. This demonstrated its capacity and put its export seal on the world. Germany has brought the U-boat name into the 21st century with the new Type 212; it 212 features an air-independent propulsion system using hydrogen fuel cells. This system is safer than previous closed-cycle diesel engines and steam turbines, cheaper than a nuclear reactor, and quieter than either. While the Type 212 is also being purchased by Italy and Norway, the Type 214 has been designed as the follow-on export model and has been sold to Greece, South Korea, and Turkey, and based on it would get the Type U 209PN sold to Portugal. In recent years Germany introduced new models such as the Type 216 and the Type 218, the latter being sold to Singapore. In 2016, Germany commissioned its newest U-boat, the U-36, a Type 212. See also List of U-boats of Germany List of U-boats never deployed List of successful U-boats Das Boot, 1981 German U-boat film Greyhound, 2020 American war film Decoys Bold (decoy) Sieglinde (decoy) Karl Dönitz List of Knight's Cross recipients of the U-boat service Orkney Wireless Museum contains an example of a U-boat radio I-boat, Japanese equivalent References Further reading Abbatiello, John (2005) Anti-Submarine Warfare in World War I: British Naval Aviation and the Defeat of the U-Boats Buchheim, Lothar-Günther. Das Boot (original German edition 1973, eventually translated into English and many other Western languages). Movie adaptation in 1981, directed by Wolfgang Petersen Gannon, Michael (1998) Black May. Dell Publishing. Gannon, Michael (1990) Operation Drumbeat. Naval Institute Press. Gray, Edwyn A. (1994) The U-Boat War, 1914–1918 Hans Joachim Koerver (2010) German Submarine Warfare 1914–1918 in the Eyes of British Intelligence, LIS Reinisch, Kurson, Robert (2004) Shadow Divers: The True Adventure of Two Americans Who Risked Everything to