When new rules in the railway operating regulations allowed higher axle loads and thus made more powerful locomotives possible, the S 9 was developed in Prussia. As with the S 7, the design was carried out as an Atlantic locomotive (wheel arrangement 4-4-2), but being 14.5 tonnes heavier. Although superheated steam technology had been used across the board in most new locomotives in other German states since about 1905, no experiments were initially wanted with the S 9 and it was developed as a saturated locomotive. A four-cylinder compound engine was used for this in order to enable better utilization of the live steam.

The firebox was extraordinarily generously dimensioned and had a grate area of four square meters, which was even a third larger than that of the later S 10. The power was ultimately limited by the cylinders, since these could only convert a certain amount of steam depending on the speed.

Two almost identical locomotives were designated as S 8. In reality, these were S 9s that had been fitted with superheaters in 1913 and 1914. Their number remained at two, since it was not assumed that there would be a clear advantage in converting all the remaining engines.

Schematic drawing with dimensions

Locomotive Magazine, February 1911

It was mainly used on the line between Berlin and Hanover. As with all four-coupled passenger and express locomotives, it was already evident before the outbreak of the First World War that these were no longer up to the demands of the rapidly growing traffic. Since some units had to be handed in as reparations after the war and some were decommissioned in the period that followed, only three machines came to the Reichsbahn. These were the two S 8 with the numbers 14 001 and 14 002 and a single S 9, which became 14 031.