Described as "an articulate and immensely self - confident gunner", Nivelle played a key role in defeating German attacks during the Alsace Offensive, the First Battle of the Marne, and the First Battle of the Aisne, as a result of the intense artillery fire he organised against them. Consequently, he was promoted to become a general in October 1914. In 1916 the Battle of Verdun occurred (21 February – 18 December), during which Nivelle was a subordinate to Philippe Pétain. When Pétain was promoted to the command of the French Central Army Group, Nivelle was promoted to Pétain's previous command of the French Second Army, which was fighting against the Germans at Verdun, and he took direct control of the army on 1 May 1916.

Nivelle is considered to have squandered the lives of some of his soldiers in wasteful counter - attacks during the Battle of Verdun; only one fresh reserve brigade was left with Second Army by 12 June. After Fleury was captured by the Germans on 23 June, Nivelle issued an Order of the Day which ended with the now famous line: Ils ne passeront pas! (They shall not pass!). Nivelle ordered the employment of a creeping barrage when the French made their initial counter - strike on 24 October. The artillery supporting the infantry focused more on suppressing German troops as opposed to destroying specific objects. These tactics proved to be effective as Fleury was captured on 24 October, as well as Fort Douaumont, a building whose capture by the Germans on 25 February 1916 was highly celebrated in Germany. Nivelle's successful counter - strikes were an important factor behind the decision to appoint him to become the commander - in - chief of the French armies on 12 December 1916.

Nivelle believed that a large saturation bombardment, followed by an extensive creeping barrage and by aggressive infantry assaults, would be able to break the enemy's front defences and help his troops reach the German gun line during a single attack, which would be followed by a breakthrough within two days. In 1917, Nivelle proposed that French forces should attack the Germans on the Aisne, keeping 27 divisions in reserve to exploit the rupture of the German defences that was expected to occur as a result, after British and other French forces had launched preliminary attacks between Arras and the Oise to keep German reserve troops occupied. Haig, the British commander, had reservations about Nivelle's plan, and supported it only in general terms and only as long as planned British operations in Belgium were not curtailed. Looking for an alternative to more months of attrition warfare, British and French political leaders supported Nivelle's proposal. For this offensive, Haig would be subordinate to Nivelle.

Between 16 March and 20 March 1917, the Germans withdrew from the Noyon salient and a smaller salient near Bapaume. French General Franchet d'Esperey, commander of the Northern Army Group, asked Nivelle if he could attack the Germans as they withdrew. Nivelle believed that that action would disrupt his operational plan, and refused d'Esperey's request as a result. Nivelle has since been deemed to have missed his only real opportunity to disrupt the German withdrawal. Haig's confidence in Nivelle's planned offensive did not improve when Paul Painlevé was appointed to become the French Minister of War in March 1917, as Painlevé had little faith in Nivelle's concepts. Philippe Pétain, over whose head Nivelle had been promoted to become commander - in - chief, wanted to launch a major attack against the Germans near Reims. The proposal is considered to have likely resulted in considerable difficulties for the Germans, but Nivelle refused because Petain's offensive would delay Nivelle's offensive for two weeks. General Micheler, commander of the French Reserve Army Group, which was to exploit the expected breakthrough on the Aisne, had serious misgivings about the upcoming battle. In a letter to Nivelle on 22 March, Micheler argued that the French might not break through as quickly as Nivelle wanted, as the Germans had reserves available, and had strengthened their defenses along a key sector of the Aisne. The other commanders of the French army groups also had concerns, but Nivelle did not make any major adjustments to his plan.

Assisted by Colonel (and former Minister of War) Messimy, Micheler communicated his worries to Prime Minister Alexandre Ribot. On 6 April, Nivelle met with Micheler, Pétain and several politicians, including President Poincaré and Minister of War Painlevé at Compiegne.

Painlevé argued that the Russian Revolution meant that France should not expect any major help from Russia, and that the offensive should be delayed until American forces were available. Americans could get involved. Micheler and Petain said that they doubted the French force allocated to the attack could penetrate beyond the second line of the German defences, and suggested a more limited operation. Poincaré, summing up the discussions, said that the offensive should proceed, but that it should be halted if it failed to rupture the German front. At this point, Nivelle offered to resign if his plan was not accepted but the politicians declared their complete confidence in him. Thus Nivelle's plan went unchanged despite the doubts expressed by the other generals and he was under greater pressure to achieve decisive results.

On 4 April, during a German attack south of the Aisne, the secret plans of the French assault were captured but Nivelle did not alter his course. The Nivelle Offensive began on 16 April 1917. It started a week after British forces had attacked near Arras. Nivelle made several declarations which improved the morale of the French troops involved in the Nivelle Offensive. Due to the fact that the preliminary bombardment against the Germans was markedly less effective than expected, and the lack of a sufficient number of French howitzers, the desired French breakthrough was not achieved on the first day of the operation, despite the use of 128 tanks. By 20 April, the French had 20,000 prisoners and 147 guns, which is considered to be "impressive results by the standards of previous years." However a decisive breakthrough on the Aisne had not been achieved. The French had suffered 96,125 casualties by 25 April, the offensive had led to a shell shortage in France, the French medical services broke down, and the delay of transporting French wounded from the front-line was demoralising.

By the end of its first week, the attack was stalled, and Nivelle was losing control. Micheler convinced Nivelle to reduce the scope of the offensive, with the goal now only to secure all of the Chemin des Dames and capture Reims. Nivelle became increasingly depressed over the course of the offensive as his orders were under a great degree of scrutiny by the French government. On 29 April, Nivelle's authority was undermined by the appointment of Pétain as Chief of the General Staff, and thus the main military adviser to the government. Although the French captured parts of the Chemin des Dames on 4–5 May, this was not sufficient to "repair Nivelle's crumbling reputation."

When the offensive ended on 9 May, 187,000 French casualties had been sustained. Although this was much less than the casualties in the Battle of Verdun, Nivelle had predicted a great success, and the country was bitterly disappointed. Petain replaced Nivelle as Commander - in - Chief on 15 May. In December Nivelle was sent to serve in Africa. He returned to France after the end of the First World War in November 1918, retiring from the military in 1921. He died on 22 March 1924.

Nivelle has come under a notable degree of criticism for some of his actions during the First World War. Julian Thompson contends that Nivelle was "careless of casualties," that he was a "disastrous choice to succeed Joffre as commander - in - chief," and that the planning for the Nivelle Offensive was "slapdash". In the book World War 1: 1914 – 1918, the execution of the Nivelle Offensive is considered to have been "murderous." David Stevenson says that the attack on the Chemin des Dames was a "disaster."

Nivelle is also considered positively in some ways. In The Macmillan Dictionary of the First World War, he is described as "a competent tactician as a regimental colonel in 1914", that his creeping barrage tactics were "innovative", and that he was able to galvanize "increasingly pessimistic public opinion in France" in December 1916." J Rickard believes Nivelle's push for a greater development of the tank contributed to its improvement by 1918, and he also says that Nivelle was a "gifted artilleryman".

The Nivelle Offensive is blamed by some historians for starting the French army mutinies of 1917. Tim Travers states that "the heavy French casualties of the Nivelle offensive resulted in French army mutinies", and David Stevenson proposes that "the Nivelle offensive - or more precisely the decision to persist with it - precipitated the French mutinies of May and June [1917]."

Mount Nivelle on the Continental Divide in the Canadian Rockies was named for him in 1918; summits with the names of other French generals are nearby: Cordonnier, Foch, Joffre, Mangin, and Pétain.