Before World War II, the development of diesel locomotives at the Deutsche Reichsbahn was in an experimental to early production phase. While the focus of mainline service was on steam and electric locomotives, the Reichsbahn—particularly from the mid-1930s onward, often in response to Wehrmacht orders—pushed forward with the standardization of small locomotives and the first medium-duty diesel-mechanical or diesel-hydraulic switching locomotives.
An Overview of Diesel Locomotives
| Series | Abbildung | Wheel arrangement | Power | Note |
| Kö I | B | 40-50 PS | Light Shunting Locomotive Series (from 1930/1932) | |
| Kö II | B | 90-128 PS | The Most Commonly Built Pre-War Shunting Locomotive with a Chain Drive | |
| V 20 | B | 200 PS | Originally Wehrmacht model WR 200 B 14 | |
| V 36 | C | 360 PS | Originally a Wehrmacht model WR 360 C 14, often used for shunting duties | |
| V 140 001 | 1’B1’ | 1.400 PS | The only mainline diesel locomotive (ex V 16 101) | |
| V 120 001 | 2’C2’ | 1.200 PS | Diesel-Pneumatic Test Locomotive (1929) |