The Second Battle of Ypres was fought between the Entente forces and the German Empire on the Western Front of World War One. The battle was fought for the control of the strategically important Belgian town of Ypres, located in Flanders. It marked the first time the German Army used poison gas as a weapon on the Western Front. Although the Germans achieved an initial breakthrough, the British managed to hold the line.
General Falkenhayn had decided to renew pressure on the Ypres salient, partly in order to disguise the transfer of troops to the Eastern Front for the forthcoming offensive at Gorlice-Tarnow, and partly to experiment with the new gas weapon. The attack was to be a limited offensive, since Falkenhayn knew that his hopes of achieving decision in the west had to be postponed as long as Generals Hindenburg and Ludendorff could effectively divert the movement of strategic reserves to the Eastern Front. Nevertheless, he hoped to gain ground and secure a more commanding position on the Channel coast.
The German Fourth Army launched an attack at Ypres employing some 168 tons of chlorine released from thousands of steel bottles in cloud form. The German troops were equipped with simple respirators. In consequence, the men of the French units holding the northern sector of the salient were caught completely unawares with no protective masks. The chlorine invaded their bodies, burning and choking them and destroying their lungs. In the end the German attack was stopped by Canadian troops stationed in the area.
The British moved up reserves to bolster General Horace Smith-Dorrien’s Second Army, which had overall responsibility for most of the Ypres Salient. Among these reserves were a significant number of battalions of the Territorial Army. These units were part of a long-standing British tradition of part-time soldiers, originally in various forms of militia, but reorganized in 1908 to create volunteer battalions within the county regiments. Many of the British counterattacks ordered by Sir John French had little chance of success. But when the Germans resumed the offensive they found that the British lines generally held firm.
Aware that German gunners could now shell the Salient from the left rear, Smith-Dorrien urged withdrawal to a more defensible 'GHQ Line' to the east of Potijze and Wieltje and within 2,000 yards of Ypres. The suggestion was rejected by Sir John French, who was in an optimistic mood following a promise of extra divisions from Foch. With his doubts about Smith-Dorrien re-awakened, French immediately transferred responsibility for all British troops around Ypres to the V Corps commander, Herbert Plumer. This incident precipitated Smith-Dorrien's resignation and he was succeeded in command of Second Army by Plumer.
The Germans carried out four more gas attacks, seizing additional ground on the Frezenberg and Bellewaarde ridges. When the battle ended, the Ypres Salient – now less than three miles deep – had assumed the basic form it would keep for the next two years.
The fighting stirred up at Ypres did not die down for months, during which time British casualties were 60,000, their ill-considered counterattacks swelling the numbers, while the Germans were estimated to have lost 35,000 dead, wounded and missing. In the end the British had no choice but to withdraw from the extremities of the salient exposed by the initial German breakthrough. At great cost a new line was carved out which, although tested time and time again by the Germans, did hold.