1945
On 6 April 1945 the factory was occupied by American troops. All aeroengine development output was transferred under great secrecy to the USA.

1940
Research in two-stroke engines was relocated from Cologne to Oberursel. Development of two-stroke engines in Oberursel was led by Dr. Ing. Adolf Schnürle, who developed the DZ 700 8-cylinder radial engine, the DZ 710 16-cylinder boxer engine and the DZ 720 32-cylinder H engine, all of them two-stroke diesel engines.

1938
Motorenfabrik Oberursel changed its name as a result of a merger between Humboldt-Deutz Motoren AG and Klöcknerwerken AG: from now on the company was known as Klöckner-Humboldt-Deutz AG, Oberursel plant. Engine production was expanded.

1935
Beginning of development work on a new diesel aeroengine, which went on to last for over two decades with interruption.

1934
The factory was reopened, initially with a workforce of 23, concentrating on the manufacture of small parts until the plant was fully equipped. The engine production resumed in summer.

1932
The factory was closed in spring. Only 5 workers were kept on for an indefinite period, as guards. The production of PM engines was relocated to Cologne due to rationalisation.

1930
Merger with Humboldt-Deutz Motoren AG. Production was resumed of products produced up to now.

1927
Beginning of development work on a new diesel aeroengine which would last over two decades with interruptions. The factory was also modernised with the introduction of American-style assembly lines.

1925
The factory was modernised with the introduction of American-style assembly lines.

1923
Development of so called PM (Permanent magnet) engines which were later fitted in a number of models and in large numbers. These engines were widely used as energy source for industrial plants, but also to power ships and their auxiliary machines.

1921
Merger with Gasmotorenfabrik Deutz AG. Motorenfabrik Oberursel lost its independence. Deutz moved the construction of two-stroke diesel engines to Oberursel.