Amid the disruption of the new rearmament plan, the disorganised and poorly trained Belgian soldiers would benefit from a central position, to delay contact with an invader but it would also need fortifications for defence, which were on the frontier.

German planning was determined by numerical inferiority, the speed of mobilisation and concentration and the effect of the vast increase of the power of modern weapons.

Frontal attacks were expected to be costly and protracted, leading to limited success, particularly after the French and Russians modernised their fortifications on the frontiers with Germany.

Alfred von Schlieffen, Chief of the Imperial German General Staff (Oberste Heeresleitung, OHL) from 1891–1906, devised a plan to evade the French frontier fortifications with an offensive on the northern flank, which would have a local numerical superiority and obtain rapidly a decisive victory.

[9] Liège is situated at the confluence of the Meuse which, at the city, flows through a deep ravine and the Ourthe River, between the Ardennes to the south and Maastricht (in the Netherlands) and Flanders to the north and west.

The main defences were a ring of twelve forts 6–10 km (3.7–6.2 mi) from the city, built in 1892 by Henri Alexis Brialmont, the leading fortress engineer of the nineteenth century.

The heavy guns and quick-firers used black powder ammunition, long superseded in other armies, which raised clouds of smoke and obscured the view of the gunners.

Provision had been made for the daily needs of the fortress troops but the latrines, showers, kitchens and the morgue had been built in the counterscarp, which could become untenable if fumes from exploding shells accumulated, because the forts were ventilated naturally.

The fortress troops were not at full strength and many men were drawn from local guard units, who had received minimal training due to the reorganisation of the Belgian army begun in 1911, which was not scheduled to be complete until 1926.

[10] In August 1914, the Germans realised that the garrison at Liège would be larger than anticipated and that prompt mobilisation had given the Belgians time to make progress on the defences between the forts.

On the night of 5/6 August the force was to make a surprise attack, penetrate the fortress ring, capture the town and the road and rail facilities.

[19] The advance into Belgium took place in suffocating hot weather; roadblocks slowed German progress; cavalry found that the bridge at Visé had been blown and were engaged by small-arms fire from the west bank.

Jäger pushed the Belgians out of the village but the bridging train of the 34th Brigade was delayed and fire from the Liège forts made the area untenable.

The 14th and 11th brigades reached their objectives with some fighting at Forêt and in the south, the 9th Cavalry Division rested its horses and held the crossings of the Ourthe and Amblève rivers.

[20] By the evening of 5 August, the coup de main was ready but it was obvious that no surprise could be obtained, given the resistance of the Belgian army "and civilians" in densely populated country, where movement had been slowed by hedges and fences.

The terrain made an advance across country impractical, so the attackers were to form marching columns behind vanguards, with slung rifles only to be used on officers' orders; white armbands and a password ("Der Kaiser") were to be used for recognition.

The force was bombarded by the guns of forts Wandre and Barcheron at a defensive position beyond Argenteau, where disorganisation and confusion led to the Germans firing on each other as well as the Belgians.

[27][d] Uncertainty about the flanks led Wachter to order a retirement to ravines east of Magnée, to gain cover against the bombardment from forts Pieron and Chaudfontaine.

An engagement began in woods east of Fort Boncelles; Hülsen was wounded and Belgian small-arms fire at the rear of the column, threw it into confusion.

Attempts were made to contact flanking units but communications to the rear had been cut and no ammunition had been delivered, which left the force of c. 1,500 men isolated during the night.

[30] On the morning of 5 August, Captain Brinckman, the German Military Attaché at Brussels, met the Governor of Liège under a flag of truce and demanded the surrender of the fortress.

Alarmed by gunfire in the street, Léman and his staff rushed outside and joined the guard platoon fighting the raiding party, which was driven off with twenty dead and wounded left behind.

[10] Léman believed that units from five German corps confronted the defenders and assembled the 3rd Division between forts Loncin and Hollogne to begin the withdrawal to the Gete during the afternoon and night of 6/7 August.

For 18 days, Belgian resistance in the east of the country had delayed German operations, which gave an advantage to the Franco-British forces in northern France and in Belgium.

In Graf Schlieffen und der Weltkrieg (1921) Wolfgang Förster wrote that the German timetable of deployment had required its armies to reach a line from Thionville to Sedan and Mons by the 22nd day of mobilisation (23 August), which was achieved ahead of schedule.

[38] John Buchan wrote The triumph was moral – an advertisement to the world that the ancient faiths of country and duty could still nerve the arm for battle and that the German idol, for all its splendour, had feet of clay.

[43] In 1926 James Edmonds, the British official historian, recorded that General Alexander von Kluck had considered that a delay of 4 to 5 days had been caused by the resistance of the Liège garrisons.

[38] In 1934, the British historian Charles Cruttwell, wrote of "brave Belgian resistance" at Liège, which surprised the Germans but did not interfere with their plans and that demolitions of railway tunnels and bridges were a more serious cause of delay.

OHL had, on the same day, ordered the 2nd Army units assembled near the Belgian border, to advance and send mixed brigades from the IX, VII and X corps to Liège immediately.

The Namur garrison withdrew at midnight to the south-west and eventually managed to rejoin the Belgian field army at Antwerp; the last fort was surrendered on 25 August.