Émile Driant was the first high-ranking casualty in the largest  and longest battle of the First World War on the Western Front between the German and French armies, fought when?
Émile Driant: Émile Augustin Cyprien Driant (11 September 1855 – 22 February 1916) was a French writer, politician, and army officer. Émile Driant:  He was the first high-ranking casualty of the Battle of Verdun during World War I. Battle of Verdun: The Battle of Verdun ("Bataille de Verdun", ] , "Schlacht um Verdun", ] ), fought from 21 February to 18 December 1916, was the largest and longest battle of the First World War on the Western Front between the German and French armies.
from 21 February to 18 December 1916