Halabja poison gas attack happened on 1988-03-16.
tear gas
Germany
Whenever there was a gas attack or the prospect of a gas attack.
His enemies were already prepared for a poison attack because it was used so much in World War One. In Britain for example, every household, school and so on was given gas masks.There wasn't any real value to using gas. It is deadly, yes, but any nation has the ability to create poisons. A poison attack on a civilian population would result in a revenge or counter attack also using poison against Germans.Hitler had fought in World War One where he had witnessed the effects of gas attacks against both his comrades and the Allies. It is believed that Hitler, despite his other atrocities, was too scarred by his experiences with the gas in World War One to consider using it.Poison gas was considered the "weapon of mass destruction". Much like nuclear warheads today - they were used as a defensive counter-measure. As if to say "do this to us and we can do the same back to you". Similar to point 2.
The gas mask
I am not 100% sure but this is very similar to the Sarin Gas attack in the Tokyo subway.
Gas attack at Hulluch happened on 1916-04-27.
Poison gas was first used during this battle
Sarin gas attack on the Tokyo subway happened on 1995-03-20.
Poison gas was never a decisive military weapon, since it is very unpredictable. A change in the direction of the wind can cause the gas that you were using to attack the enemy, to blow back in your direction and kill you instead. Nonetheless, poison gas is still feared, and armies continue to be equipped with gas masks, just in case.
For the same reason any other attack happens. To gain victory over the enemy.
The gas attack in Syria occurred on April 4, 2017, in the town of Khan Sheikhoun in Idlib province. This attack resulted in significant civilian casualties and prompted international condemnation.
to poison stuff
Poison gas and blistered your skin and burned your eyes and that is the reason they wore gas masks
poison gas is no longer allowed in warfare.
poison
Because poison gas was used against soldiers in the trenches in WWI, gas attack was feared in WWII. Poison gas was rarely used in WWII, except in the German death camps, where 11 million people (including 6 million Jews) were gassed to death. Poison gas in not an effective weapon in combat, if it rains the rain can disperse it, and the wind can blow it back at the side that's using it.