The battle of the Lys was the second of General Ludendorff’s offensives of 1918, designed to win the war before the ever-increasing number of American troops in France could enter the fighting. His first effort, the second battle of the Somme (21 March-5 April) had threatened drive a wedge between the British and French lines, but the situation had been restored after the appointment of General Foch as overall Allied commander on the Western Front.
The River Lys formed the boundary between General Horne’s First Army (south of the river) and General Plumer’s Second Army (north of the river). The German plan was for General Quast’s Sixth Army to attack south of the Lys on 9 April, and drive north west to the rail centre at Hazebrouck, while General von Armin’s Fourth Army would attack between the Lys and Ypres.
The battle was preceded by a well planned artillery bombardment, lasting from the evening of 7 April until 4 am on 9 April. Once the bombardment was over, Quast’s army attacked. The brunt of their attack fell on the 2nd Portuguese Division, close to Nueve Chapelle, which collapsed under the strain, retreating five miles. Horne was forced to pull his entire line back to prevent a gap developing.
On 10 April von Armin’s Fourth Army launched their attack. The village of Messines changed hand yet again, having been fought over in the three battles of Ypres. The Germans were only five miles from Hazebrouck. Haig requested reinforcements from the new Allied commander, but Foch was unwilling to move troops north, and was also having some problems with Pétain, whose would have had to provide the reinforcements.
On 11 April Haig issued his famous “backs to the wall” order – “with our backs to the wall and believing in the justice of our cause each us must fight on to the end”. Perhaps more important was the arrival of reinforcements in the shape of the 5th and 33rd British Divisions and the 1st Australian Division. On 14 April Foch was promoted to General-in-Chief of the Allied Armies, giving him enough authority to move French units to the Lys.
Despite this help, Plumer was forced to withdraw from the Passchendaele Ridge. On 25 April the Germans achieved their last major successes of the battle, capturing Mount Kemmel. A final attack on 29 April captured another high point, the Scherpenberg, but the general progress of the attack on 29 April convinced Ludendorff to call off the offensive.
Both sides suffered heavy losses during the battle of the Lys. The Germans lost 120,000 of the 800,000 men engaged in the battle, while British and French losses had been on the same scale. Once again Ludendorff had failed to achieve his main target. In some respects the main impact of the battle of the Lys came after the war. The only significant achievement of the dreadful fighting during the third battle of Ypres (1917) was the seizure of Passchendaele Ridge. Now in twenty days everything gained in 1917 had been lost. The fighting on the Lys in 1918 made the fighting around Ypres in 1917 look even more futile. Ironically the fighting of 1918, despite causing a short term crisis, caused critical damage to the German army, and helped to prepare the way for the great Allied counterattacks of the last hundred days of the war.