At the outbreak of World War I, anti-mine warfare was a quite young task for the navies of their time. Ten years earlier, the Russian-Japanese war showed the effectiveness of mines as a anti ship weapon. Therefore it is not very surprising that the German Navy started to build special designed ships for anti-mine warfare.
The first mine sweepers were old torpedoboats which were not usable for offensive operations anymore. Although many of those boats were used at the beginning of the war, it soon got obvious that a special build ship was needed to commit anti-mine warfare more effectively.
As a result, over 130 mine sweepers were build from 1914 to the end of the war. Because of their simple, but effective design, many of the surviving ships were used even in World War II, some of them as mine sweepers, and many of them converted for other tasks.