German Armies Approach Brussels 99 During the first two or three days of the fighting about Liege Belgian field forces assisted in the resist- ance. But as German masses came up and began to cross the Meuse, above and below, the Belgian troops, apart from the garrison, were drawn out. This en- abled the Germans to enter the city between the forts. Meantime, the Belgian field army, now if fully mobil- ized, numbering at least 80,000 took up the work of holding back German advance. The series of " battles in Belgium " which fol- lowed has already been described. With Liege squarely in its path, the German General Staff had for some days a difficult problem of getting troops west of the Meuse in large numbers and supplying them. Until it had succeeded in constructing roads and bridges north and south of the city only its cav- alry was able to pass, and they had a trying experi- ence dealing with Belgian infantry and artillery, well placed at important points between Liege and Brus- sels. Indeed, unsupported by infantry, the German cavalry could hardly be expected to perform this task very completely. On the other hand, just as soon as German In- fantry could come up, both along the Aix-la-Chapelle- Liege-Brussels line and south of the Meuse by Huy, it was certain to force the far weaker Belgian Army back. By August 18 the pressure of the German masses had become unmistakable and the Belgian force was back on the last line In front of Brussels from Louvain to Wavre and Ottignies and the