German military operations in Belgium were intended to bring the 1st, 2nd and 3rd armies into positions in Belgium, from which they could invade France, which led to sieges of Belgian fortresses along the Meuse river at Namur, after the fall of Liège on August 7 and the surrender of the last forts on 16–17 August. The government abandoned the capital, Brussels, on August 17 and after fighting on the Gete river, the Belgian field army withdrew westwards, to the National Redoubt at Antwerp on August 19. Brussels was occupied the next day and Namur was besieged on August 21.
After the battles of Mons and Charleroi, the bulk of the German armies marched south into France, leaving small forces to garrison Brussels and the Belgian railways. The III Reserve Corps advanced to the fortified zone around Antwerp and a division of the IV Reserve Corps took over in Brussels. The Belgian field army made several sorties from Antwerp in late August and September, to harass German communications and to assist the French and the British Expeditionary Force (BEF), by keeping German troops in Belgium. German troop withdrawals to reinforce the main armies in France, were postponed to repulse a Belgian sortie from 9–13 September and a corps in transit was retained in Belgium for several days. Belgian resistance and German fear of francs-tireurs, led the Germans to implement a policy of schrecklichkeit ("frightfulness") against Belgian civilians soon after the invasion, in which massacres, executions, hostage taking and the burning of towns and villages took place and became known as the Rape of Belgium.