This article describes the international seismological cooperation at the start of the last century and how this cooperation changed due to WWI. These changes were the direct reasons leading to the foundation of the Deutsche Seismologische Gesellschaft (DSG) in 1922, which changed its name to the Deutsche Geophysikalische Gesellschaft (DGG) 2 years later. It then describes the further development of the relationship between German geophysicists and their colleagues until the start of WWII.