The calculated distance (air line) between Dortmund and Forchies-la-Marche is approximately 156 miles respectively 251 kilometers.
By car or train, the actual journey to Forchies-la-Marche is certainly longer, as only the direct route (as the crow flies) between Dortmund and Forchies-la-Marche has been calculated here.
Air line (approximately)
251 kilometers
135 nautical miles