[DOC] [TLE] Second Battle of Ypres - Wikipedia [PAR] During World War I, the Second Battle of Ypres was fought from 22 April  25 May 
1915 for control of the strategic Flemish town of Ypres in western Belgium after 
the First Battle of Ypres the previous autumn. It was the first mass use by 
Germany of poison gas on the Western Front. .... The German Army first used 
chlorine-gas cylinders in April 1915 against the... [DOC] [TLE] Chemical weapons in World War I - Wikipedia [PAR] It was a vesicant that was introduced by Germany in July 1917 prior to the Third 
Battle of Ypres. The Germans marked their shells yellow for mustard gas and 
green for chlorine and phosgene; hence they called the new gas Yellow ... with 
gas in Palestine during the Second Battle of Gaza. [DOC] [TLE] First World War.com - Battles - The Second Battle of Ypres, 1915 [PAR] The Second Battle of Ypres comprised the only major attack launched by the 
German forces ... Begun in April and used primarily as a means of diverting Allied 
attention from the ... Although introduced with minimal effect on the Russian 
Eastern Front at ... the German infantry who followed up the release of the 
chlorine gas. [DOC] [TLE] Second Battle of Ypres begins - Apr 22, 1915 - HISTORY.com [PAR] On this day in History, Second Battle of Ypres begins on Apr 22, 1915. ... of 
German attack troops but instead were thrown into panic when chlorine gas 
wafted ... The introduction of poison gas, however, would have great significance 
in World War I. ... In all, more than 100,000 tons of chemical weapons agents 
were used in... [DOC] [TLE] Trenches on the Web - Special: The Second Battle of Ypres, Apr-1915 [PAR] Gas was often a double-edged sword capable of blowing back to its point of 
origin. ... greatest defensive battle ever fought by Canadian troops - the Second 
Battle of Ypres. ... with gas shells), the Germans decided to release 5700 
cylinders of chlorine ... and shell holes soldiers used as protection against 
shrapnel and bullet. [DOC] [TLE] The Battle of Ypres - History Learning Site [PAR] The Battle of Ypres (and the numerous battles that surrounded this Flanders town
) has become ... They were unaware of the size of the German force advancing 
on the town. ... They used deadly chlorine gas against defending French troops. [DOC] [TLE] Second Battle of Ypres - World War One Cemeteries [PAR] The Second Battle of Ypres was a First World War battle fought for control of the 
... It marked the first time that Germany used poison gas on a large scale on the ... 
The chlorine gas, being denser than air, quickly filled the trenches, forcing the ... 
of the 3rd Brigade arriving as they were forming, tasked to support the advance. [DOC] [TLE] How deadly was the poison gas of WW1? - BBC News - BBC.com [PAR] Jan 30, 2015 ... Gas terrified soldiers in WW1, but it killed comparatively few of them, at least on ... 
in a ghostly green cloud of chlorine at the second Battle of Ypres. ... Karl von 
Einem, commander of the German Third Army in France. ... of asphyxiating or 
deleterious gases" even before they had been used on the battlefield. [DOC] [TLE] Recalling The Trench | The Trench [PAR] After the First Battle of Ypres (autumn 1914), which frustrated German hopes of ... 
in the Ypres salient (e.g., the Second Battle of Ypres in the spring of 1915, the 
Third ... Prior to the April 1915 use of a chlorine cloud, gas shells filled with T-stoff 
... attacks from trenches took place in Belgium, but gas was used infrequently in... [DOC] [TLE] Poison gas in World War I [PAR] In what became the Second Battle of Ypres, the Germans used gas on three 
more ... In the first combined chlorine/phosgene attack by Germany, against 
British troops at ... which was introduced by Germany in July 1917 prior to the 
Third Battle of Ypres. ... When Germany launched Operation Michael on 21 
March 1918, they... [DOC] [TLE] Second Battle of Ypres in World War I - Military History - About.com

Question: In the 2nd battle of Ypres, the Germans used chlorine gas; at the 3rd battle, they introduced this gas
Answer: mustard gas