Western Front

Hindenburg line

In August 1916 the German leadership along the western front had changed as Falkenhayn resigned and was replaced by Generals Paul von Hindenburg and Erich Ludendorff. The new leaders soon recognized that the battles of Verdun and the Somme had depleted the offensive capabilities of the German army. They decided that the German army in the west would go over to the strategic defensive for most of 1917, while the Central powers would attack elsewhere.

During the Somme battle and through the winter months, the Germans created a prepared defensive position behind a section of their front that would be called the Hindenburg Line. This was intended to shorten the German front, freeing a number of divisions for other duties. This line of fortifications ran from Arras south to St Quentin. British long-range reconnaissance aircraft first spotted the construction of the Hindenburg Line in November 1916.

1917 – British Empire takes the lead

The staged withdrawal to the Hindenburg Line was named Operation Alberich by the Germans. It was begun on 9 February and completed 5 April, leaving behind a devastated territory to be occupied by the Allies. The withdrawal ranged from 10 to 50 km (6 to 31 miles) from the original front lines. This withdrawal negated the French strategy of attacking both flanks of the Noyon salient, as it no longer existed. However, offensive advances by the British continued as the High Command claimed, with some justice, that this withdrawal resulted from the battering the Germans received during the Battle of the Somme.

Meanwhile, on 6 April the United States declared war on Germany. Back in early 1915 following the sinking of the Lusitania, Germany had stopped their unrestricted submarine warfare in the Atlantic because of concerns of drawing America into the conflict. With the growing discontent of the German public due to the food shortages, however, the government resumed unrestricted submarine warfare in February 1917. They had calculated that a successful submarine siege of Britain would force that country out of the war within six months, while American forces would take a year to become a serious factor on the western front. The submarine had a brief period of success before Britain resorted to the convoy system, bringing a dramatic reduction in shipping losses.

In April 1917 the British Empire forces launched an attack starting the Battle of Arras. Despite the success of the Canadian Corps and the British 5th Infantry Division, in breaking through German lines at Vimy Ridge, the Allies could not capitalize due to losses to the south.

During the winter of 1917, German air tactics had been improved, a fighter training school was opened at Valenciennes and better aircraft with twin guns were introduced. The result was near disastrous losses for Allied air power, particularly for the British, who were struggling with outmoded aircraft, poor training and weak tactics. As a result the Allied air successes over the Somme would not be repeated, and heavy losses were inflicted by the Germans. During their attack at Arras, the British lost 316 air crews compared to 114 lost by the Germans.

French morale

The same month, French General Robert Nivelle ordered a new offensive against the German trenches. The attack, dubbed the Nivelle Offensive, would be 1.2 million men strong, to be preceded by a week-long artillery barrage and accompanied by tanks. However, the operation proceeded poorly as the French troops had to navigate through rough, upward-sloping terrain. German planes gained control of the sky making reconnaissance difficult which allowed the creeping barrage to advance too far ahead of the advancing troops. Within a week 100,000 French troops were dead. Despite the heavy casualties and his promise to halt the offensive if it did not produce a breakthrough, Nivelle ordered the attack continued into May.

On 3 May the weary 2nd French division, veterans of the Battle of Verdun, refused their orders, arriving drunk and without their weapons. Their officers lacked the means to punish an entire division, and harsh measures were not implemented. The mutinies afflicted 54 French divisions and saw 20,000 men desert. Instead, appeals to patriotism and duty encouraged the soldiers to return to defend their trenches, although they refused to participate in further offenses. By 15 May Nivelle was removed from command, replaced by General Henri Philippe Pétain, who suspended large-scale attacks. The French would go on the defensive for the next year, leaving the burden of attack to Britain and her Empire.

British offensives

On 7 July a British offensive was launched on Messines ridge, south of Ypres, to retake the ground lost in the First Battle of Ypres in 1914. Since 1915 engineers had been digging tunnels under the ridge, and 455 tonnes (1,000,000 lbs) of ammonal explosives had been planted in 21 mines under the enemy lines. Following four days of heavy bombardment, the explosives in 19 of these mines were set off resulting in the deaths of 10,000 Germans. The offensive that followed again relied on heavy bombardment, but these failed to dislodge the Germans. The offensive faltered due to the flooded, muddy ground, and both sides suffered heavy casualties.

On 11 July 1917 during this battle, the Germans introduced a new weapon into the war when they fired gas shells delivered by artillery. The limited size of an artillery shell required that a more potent gas be deployed, and so the Germans employed mustard gas, a powerful blistering agent. The artillery deployment allowed heavy concentrations of the gas to be used on selected targets. Mustard gas was also a persistent agent, which could linger for up to several days at a site, an additional demoralizing factor for their opponents. Along with phosgene, gas would be used lavishly by both German and Allied forces in later battles, as the Allies also began to increase production of gas for chemical warfare.

On 25 June the first U.S. troops began to arrive in France, forming the American Expeditionary Force. However, the American units did not enter the trenches in divisional strength until October. The incoming troops required training and equipment before they could join in the effort, and for several months American units were relegated to support efforts. In spite of this, however, their presence provided a much-needed boost to Allied morale.

In October the struggle around Ypres was renewed with the Battle of Passchendaele. Canadian veterans from the Battle of Vimy Ridge and the Battle of Hill 70 joined the depleted ANZAC and British forces and took the village of Passendale on 30 October despite extremely heavy rain which formed mud pits in the ground. Again the offensive produced large numbers of casualties for relatively little gain. The ground remained muddy and pocketed by shell craters, making supply missions and further advancement very difficult. Both sides lost a combined total of over a half million men during this offensive.

1918 – Final offensives

Following the successful Allied attack and penetration of the German defences at Cambrai, Ludendorff determined that the only opportunity for German victory now lay in a decisive attack along the western front during the spring, before American manpower became a significant presence. On 3 March 1918, the Treaty of Brest-Litovsk was signed, and Russia withdrew from the war. This would now have a dramatic effect on the conflict as 44 divisions were now released from Eastern Front for deployment to the west. This would give them an advantage of 192 divisions to the Allied 173 divisions. The German forces were also trained in the new assault tactics that had been successfully employed on the eastern front. In contrast, the Allies still lacked a unified command and suffered from morale and manpower problems.

Ludendorff's strategy would be to launch a massive offensive against the British designed to separate them from the French and drive them back to the channel ports. The attack would combine the new storm troop tactics with ground attack aircraft and a carefully planned artillery barrage that would include gas attacks.

German spring offensives

Operation Michael, the first of the German spring offensives, had very nearly succeeded in driving the French and British armies apart, advancing about 65 km during the first eight days and moving the front lines more than 100 km west, within shelling distance of Paris for the first time since 1914.

As a result of the battle, the two Allies finally agreed on a unified system of command. General Ferdinand Foch was appointed commander of all Allied forces in France. The unified Allies were now better able to respond to each of the German drives, and the offensive turned into a battle of attrition.

In May the American divisions also began to play an increasingly role, winning their first victory at Cantigny. By the summer, 300,000 American soldiers were arriving every month. A total of 2.1 million American troops would be deployed on this front before the war came to an end. The rapidly increasing American presence served as a counter for the large numbers of redeployed German forces.