There was left the roads through Belgium and Luxemburg. To come this way Germany had for more than a decade been constructing strategic railways leading from the Rhine and Moselle valleys to the Belgian frontier, double-track roads that served in a desolate country, but were provided with all the necessary machinery for detraining thousands of soldiers.
Belgium might not consent to suffer this invasion of her territory but the Belgian army was negligible, and the German heavy artillery was known to be adequate to dispose of the antiquated forts of Namur and Liege with brief delay. Once the Germans had passed the Meuse and deployed upon the Belgian plain, they could turn south and pass the Franco-Belgian frontier, which was destitute of real defenses, the few fortresses being obsolete, and thence the road ran down to Paris clear and open.
Conceivably Great Britain might make the Belgian invasion a cause for joining France. But, again, the British army was small, there was the gravest doubt as to whether it would be sent to the Continent at all, and even if it came, it would not redress the balance between the French and German armies. Such being the case, as German high command saw it, Belgium was summoned, and refusing, was attacked, the German armies passing the Belgian frontier in the direction of Liege on August 4, 1914, the day on which Germany declared war upon France, and the forty-fourth anniversary of the invasion of France in the Franco-Prussian War.
FROM THE MEUSE TO THE MARNE
To grasp the main circumstances of the opening campaign it is simplest to think of the whole German invading forces as comprising one army. The right of this army under Kluck and Bülow came west through Belgium by Brussels and Namur, swinging south after the Belgians were disposed of, and leaving a guard to curtain the Belgian army which had retreated on Antwerp. The center moved southwest through the Belgian Ardennes and Luxemburg, entering France between Longwy and Givet on the Meuse. The left moved from Metz and Strassburg, attempting to force the French barrier line between Toul and Epinal. The center was commanded by the German Crown Prince, Albert of Württemberg, and Hausen, the left by the Crown Prince of Bavaria and Heeringen. Smaller forces operating in Upper Alsace played little real part in the operations.
Taking up first the German right: It did not begin its real advance until August 12, 1914. Liege had been captured on August 7, the last fort fell on August 15. Meantime the Germans pushed a heavy screen of cavalry forward, and there was steady skirmishing between Liege and Brussels, which was magnified into battles and German defeats. In point of fact, the Belgian army was rapidly pushed back, and once the main German advance began, it fled to Antwerp.
Kluck took Brussels on August 18, 1914, and turned south, meeting the first serious resistance at Mons. Bülow, moving across the Meuse at Huy, took Namur on August 23, 1914, and his troops fought at Charleroi, while those of Hausen forced a passage of the Meuse south of Namur. The French were beaten at Charleroi, and the British while the battle of Mons was still undecided, were forced to retreat, because Bülow's success in taking Namur had imperiled the whole allied left flank.
Because he delayed his retreat too long, Sir John French was immediately threatened with destruction, Kluck having succeeded in getting on his flank, while sending superior numbers against his front. For a week there was grave danger that the Germans would be able to destroy the British and intervene between the French left and the city of Paris. At Cambrai on the 25th, British destruction seemed imminent, but the British just managed to win clear, and French troops coming up on their exposed flank by September 1, they were safe.
The French center had essayed an offensive into the Ardennes at the moment the battle of Charleroi was beginning. In this they did not succeed, and the Fourth Army under Langle de Cary fell back in perfect order from the Belgian-Luxemberg frontier across the Meuse near Sedan, where they held their line until the general retreat began. Henceforth the French armies from left to right were not seriously threatened until the final struggle at the Marne.
But the right under De Castelnau had been obliged to retreat. It had opened the campaign by a series of victories which had carried the main force into German Lorraine as far as Saarburg on the railroad from Metz to Strassburg. To the south Mülhausen had been taken, lost, and recaptured. But in the third week of August the main army encountered strong forces in the region of Morhange and fell back on Nancy, the frontier town of Lunéville being momentarily occupied by the Germans. At Nancy it stood. But its stand was one of the important battles of the western war and a contributory cause to the subsequent victory at the Marne. By this victory the eastern barrier was held and the German effort to isolate Verdun and Toul blocked. Some of the most terrible fighting of the war took place here, and the Germans, fighting under the eye of the kaiser suffered colossal losses.