At the beginning of the Second World War, there is initially enough work available. The workshop building is extended in 1940/41. However, many important employees are forced into military service, while at the same time the shortage of materials and transportation problems increase. Due to the bombing war, Wilhelm Dornbusch takes over the outsourced model construction of Klöckner-Humboldt Deutz, one of the most important customers from Cologne, in Hennef from 1944. Work can continue with restrictions until March 1945. Then the front line draws ever closer and a heavy air raid misses the factory buildings and the residential building by just a few meters.