On account of a possible under-estimation of the enemy’s strength, and of the completeness of his dispositions, the Allies found themselves, when the lines first clashed, in a more serious position than they probably anticipated.  The enemy gained two initial successes that decided, past doubt, the fate of the battle which was now raging along the whole front from Mons to Muelhouse.  Namur, the fortress which had enjoyed a reputation as the Port Arthur of Europe, fell before the weight of the German siege howitzer in a few days.  The magnitude of the disaster appalled the whole world, for indirectly the piercing of these forts laid open the road to Paris.  Nor was this all.  The enemy forced the passage of the Sambre at Charleroi, and threatened to cut the Allied centre from the left.  The British Army, on the extreme left, found itself confronted by a numerical superiority of nearly three to one, while its left flank and lines of communication with Havre were seriously menaced by a huge body of Uhlan cavalry.  In a word, the positions taken up by the whole of the Allied centre and left were no longer tenable.  To hang on would have been to court disaster.  There was nothing for it but to cut and go.

But the Allies did not meet with the same ill luck along the whole line.  The small successes gained on the right, in Alsace, had apparently been consolidated.  The German tide through Luxembourg was stemmed, and, even though the Kaiser himself witnessed its bombardment, Nancy held out.  But the trump card in the Allies’ hand was Verdun.  De Castlenau clung resolutely to the chain of forts crowning the heights in front of the town, and his successful defence saved Paris.  Whatever might happen to the centre and left, the right, at any rate, seemed safe.

The Allied Generalissimo was forced to give way before the fury of the German onslaught in Belgium.  He withdrew his armies while there was yet time, thus averting irrevocable disaster.  According to all the rules of the game, he should have retired his whole line southwards, in order to ensure the safety of Paris.  But he did not throw his highest trump:  he clung to Verdun, and left Paris exposed.  His armies retreated, not on the Capital, but in a sweeping movement that was hinged upon Verdun.  He realised that the fate of Paris depended not upon its being covered by the Allies, but upon the fate of the second great battle of the war.

Meanwhile, the great retreat—­this hinging movement—­continued, very slowly near Verdun, very, very swiftly on the left.  Days passed; no attempt was made to check the enemy’s advance, and the passing of each day left Paris more exposed.  The world gasped at the breathless swiftness with which disaster seemed to be swooping down upon the Capital.  But every day de Castlenau was consolidating his defence of Verdun, in face of tremendous odds; and every day the ferocity of the German onrush waned.  The line continued to swing resolutely back, until such time as a completed mobilisation should allow the Allies to turn upon the enemy in greater force, in their own time, and on chosen ground.  A premature effort would have spoiled all.  They had to wait for their chance.