The Battle of Armentières (also Battle of Lille) was fought by German and Franco-British forces in northern France in October 1914, during reciprocal attempts by the armies to envelop the northern flank of their opponent, which has been called the Race to the Sea. Troops of the British Expeditionary Force (BEF) moved north from the Aisne front in early October and then joined in a general advance with French troops further south, pushing German cavalry and Jäger back towards Lille until 19 October. German infantry reinforcements of the 6th Army arrived in the area during October.

The 6th Army began attacks from Arras north to Armentières in late October, which were faced by the BEF III Corps from Rouges Bancs, past Armentières north to the Douve river beyond the Lys. During desperate and mutually costly German attacks, the III Corps, with some British and French reinforcements, was pushed back several times, in the 6th Division area on the right flank but managed to retain Armentières. The offensive of the German 4th Army at Ypres and the Yser was made the principal German effort and the attacks of the 6th Army were reduced to probes and holding attacks at the end of October, which gradually diminished during November.

Background Strategic developments From the belligerents had made reciprocal attempts to turn the northern flank of their opponent. Joffre ordered the French Second Army to move from eastern France to the north of the French Sixth Army from 2 to 9 September and Falkenhayn ordered the German 6th Army to move from the German–French border to the northern flank on 17 September. By the next day, French attacks north of the Aisne led to Falkenhayn ordering the 6th Army to repulse French forces and secure the flank. When the Second Army advanced it met a German attack, rather than an open flank on 24 September. By 29 September, the Second Army had been reinforced to eight corps but was still opposed by German forces near Lille, rather than advancing around the German northern flank. The German 6th Army had also found that on arrival in the north, it was forced to oppose a French offensive, rather than advance around an open northern flank and that the secondary objective of protecting the northern flank of the German armies in France had become the main task.

Tactical developments By 6 October the French needed British reinforcements to withstand German attacks around Lille. The BEF had begun to move from the Aisne to Flanders on 5 October and reinforcements from England assembled on the left flank of the Tenth Army, which had been formed from the left flank units of the Second Army on 4 October. The Allies and the Germans attempted to take more ground after the "open" northern flank had disappeared, the Franco-British attacks towards Lille in October being followed up by attempts to advance between the BEF and the Belgian army by a new French Eighth Army. The moves of the 7th Army and then the 6th Army from Alsace and Lorraine had been intended to secure German lines of communication through Belgium, where the Belgian army had sortied several times during the period between the Great Retreat and the Battle of the Marne. In August British marines had landed at Dunkirk. In October a new 4th Army was assembled from the III Reserve Corps, the siege artillery used against Antwerp and four of the new reserve corps training in Germany.

Prelude Lille

The armament of the Lille fortress zone in 1914 consisted of and (including of rifle ammunition and guns from Paris. During the Battle of Charleroi (21 August), General d'Amade garrisoned the area from Maubeuge to Dunkirk with a line of Territorial divisions. The 82nd Division held the area between the Escaut and the Scarpe, with advance posts at Lille, Deûlémont and Tournai, just over the Belgian border. The Territorials dug in but on 23 August, the BEF retreated from Mons and the Germans drove the 82nd Territorial Division out of Tournai. The German advance reached Roubaix and Tourcoing before a counter-attack by the 83rd and 84th regiments, that reoccupied Tournai during the night. Early on 24 August, the 170th Brigade organised the defence of the bridges over the Escaut but around noon, the Territorials were forced back by a German attack. The Mayor of Lille requested that Lille be declared an open city and at the Minister of War ordered the garrison to leave the city and move between La Bassée and Aire-sur-la-Lys.

On 25 August, the German 1st Army reached the outskirts of Lille and Herment withdrew the garrison. Maubeuge to the south was defended by and the Belgian army still held Antwerp to the north. On 2 September, German detachments entered Lille and left three days later; the town was intermittently occupied by patrols guarding the right flank of the 1st Army. After the German retreat from the Marne and the First Battle of the Aisne the northward manoeuvre known as the Race for the Sea commenced and on 3 October, Joffre formed the Tenth Army ( General de Maud'huy), to reinforce the northern flank of the French armies. When the XXI Corps arrived from Champagne, the 13th Division de-trained to the west of Lille; on the morning of 4 October, Chasseur battalions of the division moved to positions north and east of Lille.

The 4th Chasseur Battalion advanced towards the suburb of Fives but was caught in small-arms fire as it left the Lille ramparts. The Chasseurs drove the Germans back from the railway station and fortifications, taking several prisoners and some machine-guns. North of the town, the French met more German patrols near Wambrechies and Marquette; the 7th Cavalry Division skirmished in the neighbourhood of Fouquet. The new Lille garrison consisting of Territorial and Algerian mounted troops, took post to the south at Faches and Wattignies, linking with the rest of the 13th Division at Ronchin. A German attack reached the railway and on 5 October, a French counter-attack recaptured Fives, Hellemmes, Flers-lez-Lille, the fort of Mons-en-Barœul and Ronchin; to the west, cavalry engagements took place along the Ypres Canal. On 6 October, the 13th Division left two Chasseur battalions at Lille as XXI Corps moved south towards Artois and French cavalry near Deûlémont repulsed a German attack. On 7 October, the Chasseur battalions were withdrawn and the defence of Lille reverted to the Territorial and Algerian troops. From 9 to 10 October, the I Cavalry Corps engaged German troops between Aire-sur-la-Lys and Armentières but failed to re-open the road to Lille.

At on 9 October, a German aeroplane appeared over Lille and dropped two bombs on the General Post Office. In the afternoon, the Germans ordered all men from of age to the Béthune Gate, with instructions to leave Lille immediately. Civilians from Lille, Tourcoing, Roubaix and neighbouring villages, left on foot for Dunkirk and Gravelines; several died of exhaustion and others were taken prisoner by German Uhlans. The last train left Lille at dawn on 10 October, an hour after German artillery had begun to fire on the neighbourhood of the station, Prefecture and the Palais des Beaux Arts. After a lull since the previous afternoon, the bombardment resumed on 11 October from until and then continued intermittently. On 12 October, the garrison capitulated, by when had been killed, many fires had been started and the vicinity of the railway station destroyed. Five companies of Bavarian troops entered the town, followed throughout the day by Uhlans, Dragoons, artillery, Death's Head Hussars and infantry.

Flanders terrain

The North-east of France and the south-west Belgium are known as Flanders. West of a line between Arras and Calais in the north-west, lie chalk downlands covered with soil sufficient for arable farming. East of the line the land declines in a series of spurs into the Flanders plain, bounded by canals linking Douai, Béthune, Saint-Omer and Calais. To the south-east, canals run between Lens, Lille, Roubaix and Courtrai, the Lys river from Courtrai to Ghent and to the north-west lay the sea. The plain is almost flat, apart from a line of low hills from Cassel, east to Mont des Cats, Mont Noir, Mont Rouge, Scherpenberg and Mount Kemmel.

From Kemmel, a low ridge lies to the north-east, declining in elevation past Ypres through Wytschaete, Gheluvelt and Passchendaele, curving north then north-west to Diksmuide where it merged with the plain. A coastal strip about wide was near sea level and fringed by sand dunes. Inland the ground was mainly meadow, cut by canals, dykes, drainage ditches and roads built up on causeways. The Lys, Yser and upper Scheldt had been canalised and between them the water level underground was close to the surface, rose further in the autumn and filled any dip, the sides of which then collapsed. The ground surface quickly turned to a consistency of cream cheese and on the coast troops were confined to roads, except during frosts.The rest of the Flanders Plain was woods and small fields, divided by hedgerows planted with trees and cultivated from small villages and farms.

The terrain was difficult for infantry operations because of the lack of observation, impossible for mounted action because of the many obstructions and difficult for artillery because of the limited view. South of La Bassée Canal around Lens and Béthune was a coal-mining district full of slag heaps, pit heads () and miners' houses (). North of the canal, the city of Lille, Tourcoing and Roubaix formed a manufacturing complex, with outlying industries at Armentières, Comines, Halluin and Menin, along the Lys river, with isolated sugar beet and alcohol refineries and a steel works near Aire-sur-la-Lys. Intervening areas were agricultural, with wide roads on shallow foundations and unpaved mud tracks in France and narrow pavé roads along the frontier and in Belgium. In France, the roads were closed by the local authorities during thaws, to preserve the surface and marked by , which were ignored by British lorry drivers. The difficulty of movement in the autumn absorbed much of the labour available on road maintenance, leaving field defences to be built by front-line soldiers.

British preparations

On 11 October, the British III Corps (Lieutenant-General William Pulteney), comprising the 4th and 6th divisions, arrived by rail at St Omer and Hazebrouck and then advanced behind the left flank of II Corps, towards Bailleul and Armentières. II Corps was to advance around the north of Lille and III Corps was to reach a line from Armentières to Wytschaete, with the Cavalry Corps on the left as far north as Ypres. French troops were to relieve the II Corps at Béthune, to move north and link with the right of III Corps but this did not occur. On the northern flank of III Corps, in front of the Cavalry Corps was a line of hills from Mont des Cats to Mt Kemmel, about above sea level.

Spurs ran south across the British line of advance and Mont des Cats and Flêtre were occupied by (HKK 4), with the 3rd, 6th and Bavarian Cavalry divisions, based at Bailleul. On 12 October, the British cavalry advanced to make room for III Corps and captured the Mont des Cats at dusk, having made combined attacks by hussars, lancers and a horse artillery battery during the day. Pulteney ordered III Corps to continue the advance on 13 October towards Bailleul, with the 6th Division on the right to move in three columns, on a line towards Vieux Berquin and Merris to the east of Hazebrouck and the 4th Division in two columns towards Flêtre, slightly north-east of Hazebrouck, with the Cavalry Corps advancing to the north east of the Mont des Cats.

German preparations