The Second World War Changes Everything
Things were really looking up for the Dassler brothers, but the arrival of another global conflict completely changed the game. World War II broke out, and Adi was called up to the Wehrmacht, while Rudolf was allowed to stay home having already served for several years in WWI.
Source: Rudolf Dassler. Source: Puma.com
Their factory was converted to supply materials for the war effort, and Adi, who had been training as a radio technician, was eventually allowed to come back home to help run the factory, heading back home to Herzogenaurach in 1941. From there, things started to go badly for the brothers.