THE PRELUDE TO THE BATTLES (a) German Movements Prior to the Battles.—The Ger man plan of campaign in 1914, which in its general lines fol lowed that drawn up some ten years before by Schlieffen, the then chief of the great general staff, involved an advance with a strong right wing through Belgium, so as to turn the fortresses on the French eastern frontier, and with the centre through the Belgian Ardennes and Luxembourg, pivoting on the fortified area Thionville-Metz. The three German right wing armies concen trated in the area between the German western frontier with Holland, Belgium and Luxembourg, and the line of the lower Rhine and Moselle from Duisburg to Treves. The I. Army (Muck) on the extreme right, comprising four first line corps and two second line corps, assembled to the north-east of Aix-la Chapelle; the II. Army (Billow) on its left, comprising three first line corps and three second line corps, to the east and south of Aix-la-Chapelle; the III. Army (Hausen), comprising three first line corps and one second line corps, to the east of the line St. Vith-Bitburg. Two cavalry corps were also allotted to the right wing, together with certain ancillary troops. In all, the three armies therefore comprised 20 first line and 12 second line infantry divisions and five cavalry divisions, and their concen tration was by Aug. 14. The fall of the last forts of Liege early on the 16th having opened the way for their advance, the I. and II. Armies crossed the Meuse between the Dutch frontier and Huy during the course of the next few , days, and came into contact with the main body of the Belgian army de ployed behind the line of the Geete between Diest and Tirle mont. By the evening of the loth the Belgians had been forced to seek shelter in Antwerp; the I. Army had occupied Brussels and the country to the south as far as Waterloo ; the II. Army on its left continued the line south-eastwards towards the Belgian fortress of Namur, which its two left wing corps were observing; and the III. Army east of the Meuse, having made its way through the northern Ardennes, was approaching the line of that river between Namur and Givet. At the headquarters of Billow, who had been placed in general control of the operations of both the I. and II. Armies, it was believed that strong French forces (about five corps) were moving forward into the angle between the Sambre and the Meuse, that the British would shortly corn plete their landing at Boulogne and move thence on Lille, though their arrival in the near future was not to be expected. On the morning of the loth Billow received orders from the German Supreme Command that his two armies should co-operate with the III. Army in an attack on the French forces west of Namur; the details of the combined attack were left to be mutually ar ranged between him and Hausen.
(b) French Movements Prior to the Battle of Charleroi.— The French V. Army, the role of which as laid down in plan 17, was to act offensively in conjunction with the IV. and III. Armies on its right, to the north of the line Verdun-Metz against the enemy right wing, concentrated on the Franco-Belgian frontier between Longwy and Hirson ; it comprised four corps (each of two divisions), two Algerian divisions, and a cavalry corps of three divisions.
The army commander, Gen. Lanrezac, from the first believed that the main strength of the forces opposed to him was to be expected north of the Meuse, and that the projected offensive across that river through the Ardennes would therefore be imprac ticable ; and he took every opportunity of impressing this view on Gen. Joffre. The latter, on the other hand, adhered to his plan for an offensive across the Meuse into the Ardennes, which he estimated would break in the enemy's centre, nullify any ad vantage gained by their right wing in Belgium, and even force its withdrawal. All he considered necessary was to extend the left wing of Lanrezac's Army to the north towards Namur and place a group of three reserve divisions behind it around Vervins. A hostile attack on Dinant on Aug. 14 and increasing evidence of the great German strength north of the Meuse finally induced him, while still maintaining his project for an offensive by the III. and IV. Armies, to move Lanrezac's Army northward to the area Mariembourg-Philippeville, so as to be in a position to meet the danger from the north.
Between Aug. 16 and 20, therefore, Lanrezac's Army carried out a change of front and a flank march which brought it to a new position south of the Sambre between the western defences of Namur and Thuin, with advanced guards holding the bridges, and one corps (I.) facing east along the Meuse between Givet and Namur to guard its right flank. Its further action as laid down by Joffre on the i8th was, in conjunction with the British and Belgian armies, either directly to oppose a hostile advance astride the Meuse between Givet and Brussels, or, if the main enemy strength lay south of that river, to act against his right flank in the northern Ardennes. On the loth, however, it became known that the Belgian army was in full retreat on Antwerp, while Sir John French had informed Lanrezac at an interview on the i 7th that the British Expeditionary Force would not be ready for action before the 24th. As regards the enemy, Lanrezac believed them to have nine or ten corps available for active operations against him north of the Meuse and another two in the angle south-east of Namur. His intention was now to close up his army on the 21st and 22nd, establish himself in a defensive position, and cross the Sambre early on the 23rd, and orders to this effect were issued on the evening of the loth.
(c) British Movements Prior to the Battle of Mons.—The mobilization of the British Expeditionary Force (B.E.F.) was completed by Aug. 9 and the transport across the Channel of its four infantry divisions and five cavalry brigades took place with out interruption between the 12th and i 7th. Field Marshal Sir John French, the commander-in-chief, had received instructions to co-operate with the French but as an independent commander only, and to be cautious of exposing his small and precious force to serious danger or losses. After a series of conferences with Joffre and Lanrezac, it was agreed that the B.E.F. should take part in Lanrezac's offensive, moving on the left of Lanrezac by Soignies on Nivelles, and as a preliminary should move forward from its concentration area east of the general line Maubeuge Landrecies-Bohain to a position of assembly about Mons. On the evening of the loth, orders were issued for the advance to begin on the morrow.