"Because they dare not leave a stronghold of that kind in their rear, as they pass through Belgium," answered Roland.
"What difference would it make?" asked Alfred.
"An enemy in a strongly fortified position in the rear, or on either flank, will always subject the advancing army to attack, but the most serious difficulty to an army under such condition is that, as the advancing army must be daily supplied with provisions and ammunition, a fortified city, like Liège, would always lay open to attack the railroad lines, which supply them, and the cutting of the lines of communication would subject them to defeat or capture."
"I did not think of that," answered Ralph.
"The General said in the first fight we had, that the Germans tried to out-flank us. What did he mean by that?" asked Ralph.
"If an enemy goes around the end of the fighting line it has out-flanked them. The object of flanking is to get behind one end of the force, and thus make it change its position or, as is most usually the case, compel the out-flanked party to fight on a front which is not provided with earthworks or other means of protection."
During all this time the bombardment continued. Sometimes it was an incessant roar. In the meantime the Germans came closer, but the city was not yet entirely surrounded. As infantry would be useless within the town, the Belgian forces were waiting outside to resist the advance of the foe, in its attempt to cross toward the border.