section_path: Progress of the war/Final years of the war/Nivelle Offensive (April–May 1917)
section_name: Nivelle Offensive (April–May 1917)
paragraph_text: Nivelle Offensive (April–May 1917)
  
  In December 1916, Robert Nivelle replaced Pétain as commander of French armies on the Western Front and began planning a spring attack in Champagne, part of a joint Franco-British operation. Poor security meant German intelligence was well informed on tactics and timetables, but despite this, when the attack began on 16 April the French made substantial gains, before being brought to a halt by the newly built and extremely strong defences of the Hindenburg Line. Nivelle persisted with frontal assaults and, by 25 April, the French had suffered nearly 135,000 casualties, including 30,000 dead, most incurred in the first two days.
  
  Concurrent British attacks at Arras were more successful, though ultimately of little strategic value. Operating as a separate unit for the first time, the Canadian Corps ' capture of Vimy Ridge is viewed by many Canadians as a defining moment in creating a sense of national identity. Though Nivelle continued the offensive, on 3 May the 21st Division, which had been involved in some of the heaviest fighting at Verdun, refused orders to go into battle, initiating the French Army mutinies; within days, "collective indiscipline" had spread to 54 divisions, while over 20,000 deserted.