114 ^^^ Great JVar for French troops in considerable force were just south of the Belgian lines at Gembloux, when the Germans, by a wide sweep to the north, broke in upon the Belgians at Louvain, threatened their line of retreat upon Antwerp and thus compelled them to retire rapidly on that city. Thus, by Thursday August 20, the Germans had accomplished the task which constituted the first phase of their operations to get at France and stood in force at Brussels while their cavalry was sweeping west and north toward Ostend and Ghent. From Brussels to France three Important lines of rail and roadway lead south to the French border some fifty miles away. That to the west enters France at Lille, where it joins the Ghent-Antwerp- Paris line. The middle line crosses the French boundary north of Valenciennes. The eastern line joins the Liege-Paris railroad at Charleroi and enters France at Maubeuge. Maubeuge and Lille are per- haps fifty miles apart and Valenciennes is almost equidistant from both. Maubeuge and Lille were fortified towns, each surrounded by a circle of de- tached forts. With Valenciennes, Conde, Le Ques- nay and Mons, the last named now in Belgium, they constituted the famous " Belgian Belt," constructed by Vauban and familiar to all students of French and English history. But only Maubeuge and Lille were now fortified. There were, however, in addition several detached forts between the two cities occupy- ing vantage points and to be reckoned with still.