Question: 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?

Context paragraphs:
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.  The battle took place on the hills north of Verdun-sur-Meuse in north-east France.  The German 5th Army attacked the defences of the Fortified Region of Verdun ("RFV, Région Fortifiée de Verdun") and those of the French Second Army on the right bank of the Meuse.  Inspired by the experience of the Second Battle of Champagne in 1915, the Germans planned rapidly to capture the Meuse Heights, an excellent defensive position with good observation for the artillery to bombard Verdun.  The Germans hoped that the French would commit their strategic reserve to recapture the position and suffer catastrophic losses in a battle of annihilation, not costly for the Germans because of their tactical advantage.

First Battle of Artois: The First Battle of Artois (17 December 1914 – 13 January 1915) was a battle fought during World War I by the French and German armies on the Western Front.  The battle was the first offensive move on the Western Front by either side after the end of the First Battle of Ypres in November 1914.  The French assault failed to break the stalemate.

First Battle of the Marne: The Battle of the Marne (French: Première bataille de la Marne , also known as the Miracle of the Marne, "Le Miracle de la Marne") was a World War I battle fought from 6–10 September 1914.  It resulted in an Allied victory against the German armies in the west.  The battle was the culmination of the German advance into France and pursuit of the Allied armies which followed the Battle of the Frontiers in August and had reached the eastern outskirts of Paris.  A counter-attack by six French armies and the British Expeditionary Force (BEF) along the Marne River forced the Imperial German Army to retreat north-west, leading to the First Battle of the Aisne and the Race to the Sea.  The battle was a victory for the Allies but led to four years of trench warfare stalemate on the Western Front.

Battle of Hürtgen Forest: The Battle of Hürtgen Forest (German: "Schlacht im Hürtgenwald" ) was a series of fierce battles fought from 19 September to 16 December 1944 between American and German forces on the Western Front during World War II in the Hürtgen Forest about 50 mi2 east of the Belgian–German border.  It was the longest battle on German ground during World War II, and is the longest single battle the U.S. Army has ever fought.

Nivelle Offensive: The Nivelle Offensive of 1917, was a Franco-British offensive on the Western Front in the First World War.  The French part of the offensive was intended to be strategically decisive, by breaking through the German defences on the Aisne front within 48 hours, with casualties expected to be around 10,000 men.  A preliminary attack was to be made by the French Third Army at St. Quentin and the British First, Third and Fifth armies at Arras, to capture high ground and divert German reserves from the French fronts on the Aisne and in Champagne.  The main offensive was to be delivered by the French on the Chemin des Dames ridge (the Second Battle of the Aisne, "La bataille du Chemin des Dames" , "Seconde bataille de l'Aisne" and "Doppelschlacht Aisne-Champagne" ), with a subsidiary attack by the Fourth Army (the Third Battle of Champagne, the Battle of the Hills or Battle of the Hills of Champagne).  The final stage of the offensive was to follow the meeting of the British and French armies, having broken through the German lines, with a pursuit of the defeated German armies towards the German frontier.

Émile Driant: Émile Augustin Cyprien Driant (11 September 1855 – 22 February 1916) was a French writer, politician, and army officer.  He was the first high-ranking casualty of the Battle of Verdun during World War I.

First Battle of Ypres: The First Battle of Ypres (French: "Première Bataille des Flandres" German: "Erste Flandernschlacht" , 19 October – 22 November) was a battle of the First World War, fought on the Western Front around Ypres, in West Flanders, Belgium, during October and November 1914.  The battle was part of the First Battle of Flanders, in which German, French and Belgian armies and the British Expeditionary Force (BEF) fought from Arras in France to Nieuport on the Belgian coast, from 10 October to mid-November.  The battles at Ypres began at the end of the Race to the Sea, reciprocal attempts by the German and Franco-British armies to advance past the northern flank of their opponents.  North of Ypres, the fighting continued in the Battle of the Yser (16–31 October), fought between the German 4th Army and the Belgian army and French marines.

Siege of Antwerp (1914): The Siege of Antwerp (Dutch: "Beleg van Antwerpen" , French: "Siège d'Anvers" , German: "Belagerung von Antwerpen" ) was an engagement between the German and the Belgian, British and French armies around the fortified city of Antwerp during World War I.  German troops besieged a garrison of Belgian fortress troops, the Belgian field army and the British Royal Naval Division in the Antwerp area, after the German invasion of Belgium in August 1914.  The city, which was ringed by forts known as the National redoubt, was besieged to the south and east by German forces.  The Belgian forces in Antwerp conducted three sorties in late September and early October, which interrupted German plans to send troops to France, where reinforcements were needed to counter the French armies and the British Expeditionary Force (BEF).

Battle of Arras (1917): The Battle of Arras (also known as the Second Battle of Arras) was a British offensive on the Western Front during World War I.  From 9 April to 16 May 1917, British troops attacked German defences near the French city of Arras on the Western Front.  The British achieved the longest advance since trench warfare had begun, surpassing the record set by the French Sixth Army on 1 July 1916.  The British advance slowed in the next few days and the German defence recovered.  The battle became a costly stalemate for both sides and by the end of the battle the British Third and First armies had suffered about 160,000 casualties and the German 6th Army 125,000 casualties.

Battle of the Somme: The Battle of the Somme (French: "Bataille de la Somme" , German: "Schlacht an der Somme" ), also known as the Somme Offensive, was a battle of the First World War fought by the armies of the British and French empires against the German Empire.  It took place between 1 July and 18 November 1916 on both sides of the upper reaches of the River Somme in France.  The battle was intended to hasten a victory for the Allies and was the largest battle of the First World War on the Western Front.  More than 3 million men fought in this battle and one million men were wounded or killed, making it one of the bloodiest battles in human history.

Supporting paragraphs: Émile Driant Battle of Verdun
Answer: from 21 February to 18 December 1916