At the end of the Great Retreat, the Race to the Sea (17 September – 19 October) began, a period of reciprocal attempts by German and Franco-British forces to outflank each other, extending the front line northwards from the Aisne, into Picardy, Artois, and Flanders.

[3] Conscription was introduced in 1909 but with a reduction in the term of service to fifteen months; the Agadir Crisis made the government continue its preparations but until 1913, the size of the army was not fixed as a proportion of the population.

[3] The German invasion of Belgium on 4 August 1914, in violation of Article VII of the Treaty of London was the casus belli, the reason given by the British government, for declaring war on Germany.

Amid the disruption of the new rearmament plan the disorganised and poorly trained Belgian conscripts would benefit from a central position to delay contact with an invader.

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.

[10] On 28 June the Austrian Archduke Franz Ferdinand was assassinated and on 5 July the Kaiser promised "the full support of Germany" if Austria-Hungary took action against Serbia.

The German government made proposals to secure British neutrality; the Admiralty sent a Warning Telegram to the Fleets and the War Office ordered the Precautionary Period.

[13] Belgian military operations in the east of the country had delayed German plans, which some writers claimed had been advantageous to the Franco-British forces in northern France and in Belgium.

[13] 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.

[13] John Buchan wrote that "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.

To block a German advance towards Hasselt and Diest, the Cavalry Division commanded by de Witte, was sent to guard the bridge over the river Gete at Halen.

During an evening meeting, the Belgian general staff directed de Witte to fight a dismounted action in an attempt to nullify the German numerical advantage.

[16] From communication intercepts, the Belgian Headquarters discovered that the Germans were heading in force towards de Witte and sent the 4th Infantry Brigade to reinforce the Cavalry Division.

[16] Belgian engineers had blown the bridge over the Gete but the structure only partly collapsed, which left the Germans an opportunity to send about 1,000 troops into the centre of Halen.

The Germans went on to besiege the fortified cities of Namur, Liège and Antwerp, which had formed the basis of the Belgian defensive system, intended to delay an invader until foreign troops could intervene, according to the Treaty of London.

The city was ringed by forts, known as the National Redoubt and was invested to the south and east by German forces, which began a bombardment of the Belgian fortifications with heavy and super-heavy artillery on 28 September.

The Belgian garrison had no hope of victory without relief and despite the arrival of the Royal Naval Division beginning on 3 October the Germans penetrated the outer ring of forts.

[23] On 9 October, the remaining garrison surrendered, the Germans occupied the city, and some British and Belgian troops escaped north to the Netherlands, where they were interned for the duration of the war.

At the battles of Picardy and Albert in late September, the French Second and German 6th armies fought meeting engagements from the Oise north to the Somme but neither was able to envelop the northern flank of the opponent.

On 8–9 October the BEF began to assemble around Abbeville, ready to begin an offensive around the German northern flank, towards the Belgian and Allied troops in Flanders.

The Belgian army was exhausted, water was so close to the land surface that trenches could only be dug 1–2 ft (0.30–0.61 m) deep and the field artillery was short of ammunition and had worn guns.

German attacks took ground on the Menin road on 29 October and drove back the British cavalry next day, from Zandvoorde and Hollebeke to a line 3 km (1.9 mi) from Ypres.

[26] The speed by which allegations of franc tireur warfare reached Germany led to suspicions of orchestration, since newspapers reported atrocities against German soldiers as soon as 5 August; on 8 August, troops marching towards the German-Belgian frontier bought newspapers containing lurid details of Belgian civilians marauding, ambushing German troops, desecrating corpses and poisoning wells.

[26] To avoid delays and minimise the detachments of garrisons to guard lines of communication, the German army resorted to schrecklichkeit (frightfulness), quickly to terrorise civilians into submission.

On some occasions, the atrocities were committed by front-line troops in the heat of the moment; other crimes were cold blooded, taking place days after the fighting had ended.

Dutch civilians heard gunfire on the night of 23 August, from Visé over the border and in the morning 4,000 refugees crossed the frontier, describing killings and the abduction of 700 men and boys for forced labour in Germany.

[52] At Dinant the French fell back on 22 August and blew the bridge; German troops repairing the crossing were ostensibly obstructed by civilians, which was allegedly witnessed by General Max von Hausen, the 3rd Army commander.

A horse entered Leuven during the night and caused a stampede, which panicked German sentries, after which General von Luttwitz, the Military Governor of Brussels, ordered reprisals.

[50] The German General Government of Belgium (Kaiserliches Deutsches Generalgouvernement Belgien), was established on 26 August 1914 with Field Marshal Colmar Freiherr von der Goltz as the Military Governor.

Falkenhayn attempted to gain a limited success after the failure of the October offensive and aimed to capture Ypres and Mt Kemmel but even this proved beyond the capacity of the 4th and 6th armies.