 As elsewhere , sabotage was employed against enemy military and economic assets , with railway lines and bridges being common targets . The activities of Groupe G , a small student resistance cell based in Brussels , alone are estimated to have cost the Nazis 10 million man @-@ hours of labour to repair damages done . Direct attacks on German troops and military installations were rarer , yet one estimate puts the number of German soldiers killed by the Belgian resistance in 1941 as higher than in all of France . 
