The Royal Württemberg State Railways had two routes with steep grades in the notorious Geislingen Grade and the rail line Bretten-Ulm. They demanded everything locomotives had to give. As train loads continuously increased in the early years of the 20th century, the state railroads required more powerful locomotives that had to have a maximum axle load of 16 metric tons. For that reason, in 1917 the designers boldly went a step further with the class K with its 6 coupled driving axles. In order to ensure good running characteristics on curves, the first and sixth axles had side play. The Esslingen Machinery Company reduced the wheel flange by 15 mm / 9/16" on the third and fourth driving axles. The two outer cylinders were connected to the fourth set of driving wheels, the two inner cylinders were connected to the third set of driving wheels. Test runs demonstrated that the locomotives offered unusually good performance on grades. On level ground, however, they were underutilized and were consequently not economical. Their service life was spent pretty much on their home routes in Württemberg. In the World War II some of these locomotives operated as far as Austria, Hungary, and Yugoslavia. In 1953, the German Federal Railway took the last class K (designated as the class 59.0 starting in 1925) locomotive out of service. In Austria these locomotives were in service until 1957 as the class 659.