Between 1908 and 1910 fourteen big boats with four torpedo tubes and two reload torpedoes were ordered. These boats used a kerosene engine which was safer than gasoline and more powerful than steam, but the white exhaust of the kerosene betrayed the presence of the U-boats, robbing them of their primary asset, their stealth. Diesel engines did not have that disadvantage, but a powerful and reliable diesel engine was still under development. Finally the class of 1912–13 had the first diesel engine installed in a German navy boat. Between 1910 and 1912 twenty-three diesel U-boats were ordered. At the start of World War I in 1914, Germany had 48 submarines of 13 classes in service or under construction. During that war, the Imperial German Navy used SM U-1 for training. Retired in 1919, she remains on display at the Deutsches Museum in Munich.
Between 1908 and 1910 fourteen big boats with four torpedo tubes and two reload torpedoes were ordered. These boats used a kerosene engine which was safer than gasoline and more powerful than steam, but the white exhaust of the kerosene betrayed the presence of the U-boats, robbing them of their primary asset, their stealth. Diesel engines did not have that disadvantage, but a powerful and reliable diesel engine was still under development. Finally the class of 1912–13 had the first diesel engine installed in a German navy boat. Between 1910 and 1912 twenty-three diesel U-boats were ordered. At the start of World War I in 1914, Germany had 48 submarines of 13 classes in service or under construction. During that war, the Imperial German Navy used SM U-1 for training. Retired in 1919, she remains on display at the Deutsches Museum in Munich