Germans Take Brussels — Start for France 117 up in the three critical days that followed the open- ing battle at Mons on August 23. This failure on the part of the French compelled the retreat of the British, before the engagement at Mons had reached a decisive stage, exposed the whole left wing of the Allied armies and made inevitable the series of dis- asters that followed so promptly. Meantime the opening of the Franco-German campaign recalled names famous once and now for- gotten in long years of peace. Jemappes, Fleurus, Wattignles had been fought on the fields over which the cavalry of three nations were already on August 20 skirmishing. At Charleroi, soon to witness a French defeat, Napoleon had beaten the Prussians in the Waterloo campaign. By the route the Germans were now taking, the Allies in 1792-3 had marched against Maubeuge and had failed to take it and get to Paris by the narrowest of margins. Before the Battle of Mons British and German cavalry actually clashed on the field where a century before Prussians and English had destroyed the last Napoleonic army. On August 22, Namur fell, on the following day the French were defeated at Charleroi, the British compelled to retire from Mons to avoid an envelop- ing movement. Lille promptly opened Its gates to the Germans. At a single thrust the Germans had broken through the first line of French defense. The campaign In Belgium had given place to the invasion of France.