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The 1918 Spring Offensive or Kaiserschlacht (Kaiser's Battle) and also known as the Ludendorff Offensive was a series of German attacks along the Western Front during World War I, which marked the deepest advances by either side since 1914. The German authorities had realised that their only remaining chance of victory was to defeat the Allies before the overwhelming human and matériel resources of the United States could be deployed. They also had the advantage of nearly 50 divisions freed by the Russian surrender (Treaty of Brest-Litovsk).

There were four separate German attacks, codenamed Michael, Georgette, Gneisenau, and Blücher-Yorck. They were initially intended to draw forces away from the Channel ports that were essential for British supply and then attack the ports and other lines of communication. The planning process, however, diluted the strategy.

Tactics
By this late stage of the war, both sides had refined their tactics.

Offensive tactics
The German army had developed stormtrooper units, with infantry trained in Hutier tactics (after Oskar von Hutier) to infiltrate and bypass enemy front line units, leaving these strongpoints to be "mopped-up" by follow-up troops. The stormtroopers' tactic was to attack and disrupt enemy headquarters, artillery units and supply depots in the rear areas, as well as to occupy territory rapidly. Each major formation "creamed off" its best and fittest soldiers into storm units; several complete divisions were formed from these elite units. This process gave the German army an initial advantage in the attack, but meant that the best formations would suffer disproportionately heavy casualties, while the quality of the formations stripped of their best personnel declined.

To enable the initial breakthrough, Lieutenant Colonel Georg Bruchmüller, a German artillery officer, developed the Feuerwalze, an effective and economical artillery bombardment scheme. There were three phases: a brief attack on the enemy's command and communications, destruction of their artillery and lastly an attack upon the enemy front-line infantry defenses. Bombardment would always be brief so as to retain surprise. Bruchmüller's tactics were made possible by the vast numbers of heavy guns (with correspondingly plentiful amounts of ammunition for them) which Germany possessed by 1918. It was possible for the Germans to launch an offensive at almost any vital part of the front without giving the Allies notice of their intentions by moving guns and shells to the threatened sector.

Defensive tactics
In their turn, the Allies had developed defenses in depth, reducing the proportion of troops in their front line and pulling reserves and supply dumps back beyond German artillery range. This change had been made after experience of the successful German use of defense in depth during 1917.

In theory, the front line was an "outpost zone" (later renamed the "forward zone"), lightly held by snipers, patrols and machine-gun posts only. Behind was the "battle zone", where the offensive was to be firmly resisted, and behind that again was a "rear zone", where reserves were held ready to counter-attack or seal off penetrations. In theory a British infantry division (with 9 infantry battalions) deployed 3 battalions in the outpost zone, 4 battalions in the battle zone and 2 battalions in the rear zone.

This change had not been completely implemented by the Allies. In particular, in the sector held by the British Fifth Army, which they had recently taken over from French units, the defences were not completed and there were too few troops to hold the complete position in depth. The rear zone existed as outline markings only, and the battle zone consisted of battalion "redoubts" which were not mutually supporting (allowing stormtroopers to penetrate between them).

Michael
On March 21, 1918 the Germans launched a major offensive against the British Fifth Army, and the right wing of the British Third Army.


 * The artillery bombardment began at 4.40 am on 21 March. The bombardment [hit] targets over an area of 150 square miles, the biggest barrage of the entire war. Over 1,100,000 shells were fired in five hours...



The German armies involved were the Seventeenth Army under Otto von Bülow, the Second Army under Georg von der Marwitz and the Eighteenth Army under Oskar von Hutier, with a Corps (Gruppe Gayl) from the Seventh Army supporting Hutier's attack. Although the British had learned the approximate time and location of the offensive, the weight of the attack and the preliminary bombardment was an unpleasant surprise. The Germans were also fortunate in that the morning of the attack was foggy, allowing the stormtroopers leading the attack to penetrate deep into the British positions undetected.

By the end of the first day the British had lost near 20,000 dead and near 35,000 wounded and the Germans had broken through at several points on the front of the British Fifth Army. After two days Fifth Army was in full retreat. As they fell back, many of the "redoubts" were left to be surrounded and overwhelmed by the following German infantry. The right wing of Third Army also retreated, to avoid being outflanked.

Erich Ludendorff, the German commander, failed to follow the correct stormtrooper tactics, as described above. His lack of a coherent strategy to accompany the new tactics was expressed in a remark to one of his Army Group commanders, Rupprecht, Crown Prince of Bavaria, in which he stated, "We chop a hole. The rest follows". Ludendorff's dilemma was that the most important parts of the allied line were also the most strongly held. Much of the German advance was achieved where it was not strategically significant. Because of this, Ludendorff continually exhausted his forces by attacking strongly entrenched British units. At Arras on March 28, he launched a hastily-prepared attack (Operation Mars) on the left wing of the British Third Army, to try and widen the breach in the Allied lines, and was repulsed.

The German breakthrough had occurred just to the north of the boundary between the French and British armies. The French commander-in-chief, General Pétain, sent reinforcements to the sector too slowly in the opinion of the British commander-in-chief, Field Marshal Haig, and the British government. The Allies reacted by appointing the French General Ferdinand Foch to coordinate all Allied activity in France and then as of all Allied forces everywhere.

After three days, the German advance began to falter, as the infantry became exhausted and it became increasingly difficult to move artillery and supplies forward to support them. Fresh British and Australian units were moved to the vital rail centre of Amiens and the defence began to stiffen. After fruitless attempts to capture Amiens, Ludendorff called off Operation Michael on April 5. By the standards of the time, there had been a substantial advance. It was, however, of little value — a Pyrrhic victory in terms of the casualties suffered by the crack troops, as Amiens and Arras remained in Allied hands. The newly-won territory was difficult to traverse, as much of it consisted of the shell-torn wilderness left by the 1916 Battle of the Somme, and difficult to defend against Allied counterattacks.

The Allies lost nearly 255,000 men (British, British Empire, French and American). They also lost 1,300 artillery pieces and 200 tanks. All of this could be replaced, either from British factories or from American manpower. German troop losses were 239,000 men, largely specialist shocktroops (Stoßtruppen) who were irreplaceable. In terms of morale, the initial German jubilation at the successful opening of the offensive soon turned to disappointment as it became clear that the attack had not achieved decisive results.

Georgette
Michael had drawn British forces to defend Amiens, leaving the rail route through Hazebrouck and the approaches to the Channel ports of Calais, Boulogne and Dunkirk vulnerable. German success here could choke the British into defeat.



The attack started on April 9 after a Feuerwalze. The Portuguese defenders at the point of attack were rapidly overrun but the British defenders on the southern flank held firm. The next day, the Germans widened their attack to the north, forcing the defenders of Armentieres to withdraw before they were surrounded, and capturing most of the Messines Ridge. By the end of the day, the few British divisions in reserve were hard-pressed to hold a line along the River Lys.

Without French reinforcement, it was feared that the remaining 15 miles to the ports could be covered within a week. The British Expeditionary Force (BEF) commander, Field Marshal Sir Douglas Haig, issued an "Order of the Day" on April 11 stating, "With our backs to the wall and believing in the justice of our cause, each one of us must fight on to the end."

However, the German offensive had stalled because of logistical problems and exposed flanks. Counterattacks by British, French, American, Canadian and ANZAC forces slowed and stopped the German advance. Ludendorff ended Georgette on April 29.

As with Michael, losses were roughly equal, approximately 110,000 men wounded or killed, each. Again, the results were disappointing for the Germans. Hazebrouck remained in Allied hands and the flanks of the German salient were vulnerable. The British abandoned the comparatively worthless territory they had captured at vast cost the previous year around Ypres, freeing several divisions to face the German attackers.

Blücher-Yorck
While Georgette ground to a halt, a new attack on French positions was planned to draw forces further away from the Channel and allow renewed German progress in the north. The strategic objective remained to split the British and the French and gain victory before American forces could make their presence felt on the battlefield.

The German attack took place on May 27, between Soissons and Rheims. The sector was partly held by six British divisions which were "resting" after their exertions earlier in the year. In this sector, the defences had not been developed in depth, mainly due to the obstinacy of the commander of the French Sixth Army, General Denis Auguste Duchêne. As a result, the Feuerwalze was very effective and the Allied front, with a few notable exceptions, collapsed. Duchêne's massing of his troops in the forward trenches also meant there were no local reserves to delay the Germans once the front had broken. Despite French and British resistance on the flanks, German troops advanced to the Marne River and Paris seemed a realistic objective. However, United States Army machine-gunners and Senegalese sharpshooters halted the German advance at Château-Thierry, with United States Marines also heavily engaged at Belleau Wood.

Yet again, losses were much the same on each side: 137,000 Allied and 130,000 German casualties (up to June 6). German losses were again mainly from the difficult-to-replace assault divisions.

Gneisenau
Ludendorff sought to extend Blücher-Yorck westwards with Operation Gneisenau, intending to draw yet more Allied reserves south and to link with the German salient at Amiens.

The French had been warned of this attack by information from German prisoners and their defence in depth reduced the impact of the artillery bombardment on June 9. Nonetheless, the German advance was impressive, despite fierce French and American resistance. At Compiègne, a sudden French counter-attack on June 11 caught the Germans by surprise and halted their advance. Gneisenau was called off the following day.

Losses were approximately 35,000 (Allied) and 30,000 (German).

Last German attack
The final offensive launched by Ludendorff on July 15 was a renewed attempt to draw Allied reserves south from Flanders, and to expand the salient created by Blücher-Yorck eastwards. An attack east of Rheims was thwarted by the French defence in depth. Although German troops southwest of Rheims succeeded in crossing the River Marne, the French launched a major offensive of their own on the west side of the salient on July 18, threatening to cut off the Germans in the salient. Although Ludendorff was able to hold off this attack and successfully evacuate the salient, the initiative had clearly passed to the Allies, who were shortly to begin the Hundred Days Offensive which effectively ended the war.

Strategic Impact
The Kaiserschlacht series of offensives had yielded large, in First World War terms, territorial gains for the Germans. However, the strategic objective of a quick victory was not achieved and the German armies were severely depleted, exhausted and in exposed positions. The territorial gains were in the form of salients which greatly increased the length of the line that would have to be defended when allied reinforcements gave the allies the initiative. In six months the strength of the German army had fallen from 5.1 million fighting men to 4.2 million. Manpower was exhausted. German High Command predicted they would need 200,000 men per month to make good the losses suffered, but even by drawing on the next annual class of eighteen year olds, only 300,000 recruits would be available for the year. Even worse, they lost most of their best trained men as "stormtroopers" tactics asked them to lead the attack. Even so, about a million German soldiers remained tied up in the east until the end of the war, attempting to run a short-lived addition to the German Empire in Europe. German political ambitions remained extravagant until the very end.

The Allies had been badly hurt but not broken. The lack of a unified high command was partly rectified by the appointment of Marshal Foch to the supreme command and coordination would improve in later Allied operations. American troops were for the first time used as independent formations and had proven themselves. Their presence counterbalanced the serious manpower shortages that Britain and France were experiencing after four years of war.