So from hour to hour the struggle went on, along roads, through woods, behind hedges and ditches, with furious rushes and counter-rushes of infantry, and dashes of cavalry; the air filled with the puffs and smoke of bursting shrapnel, the boom of battle travelling slowly over the countryside like a laggard thunderstorm with its lightnings chained to earth. To what an extent skilful troops may arrest the advance of a hostile force enormously greater in numbers has been many times exemplified in warfare. The Germans employed their overwhelming superiority in cavalry and machine guns with the greatest energy. They had to deal, however, with elusive yet bold and persistent enemies. In this part of Belgium, the country is perfectly flat. There are no hillocks to assist observation. Information by airmen was rendered unreliable by the rapid movements of the Belgian forces. Literally the invaders had to grope their way, imagining that the main army was in front of them. Beyond the narrow horizon the danger lurked, but exactly where, it was hard to say. The most serious effort on the part of the invaders was to throw a large force towards Antwerp. Against the strong position held by the Belgians and their change of front the effort failed. The assumed Belgian left wing had become its centre. Strongly posted as that now was with a deep river in front and a great fortress in the rear the position made an attack too costly to be pressed. Half at least of the whole mighty German host would have been necessary to force it. That, however, would have thrown the programme into confusion. The artillery duel went on from daylight to darkness, but the Belgians showed themselves unshakable. All the efforts of the invaders to throw troops over the Dyle were beaten off with heavy loss. Finally, the Germans were compelled to pass on, leaving the Belgian main army a still unbeaten menace. The military considerations which dictated the Belgian strategy may be readily made clear. Since the base of the army was Antwerp, where it had all its supplies and munitions, the first essential was not to be cut off from that base. An army defending its native country, and among its own people may, so far as foodstuffs are concerned, be said to be at home anywhere, but it cannot in modern warfare fight without shells and bullets, and when those it brings with it are exhausted its power as a present-day fighting force is at an end. No army can encumber itself in the field with more than the munitions it immediately needs. It has consequently to keep in touch with its reserve stocks, or, in military phrase, to keep its line of communications open. That to a general in command is as important as victory. Indeed, a victory gained if it left the communications cut would be illusory.