Wilfred Owens was a soldier, killed in battle one week before the armistice (WW2 ending).
Owens was inspired by writers such as Siegfried Sassoon who was also a war writer who critiqued patriotism and jingoistic (extreme patriotism, especially through war) attitudes.
Owens wrote his poetry to express the horror of war as opposed to internalising it.
Exposure was written in 1917, as Owens was at war in the trenches, creating an impression of salience (importance) on the reader.
Exposure contrasted the jingoistic (extreme patriotism through violence) and glamourised portrayals of war by poets such as Jessie Pope.
Owens dispelled this myth by "exposing" the harsh realities and virulence (harmfulness of a disease/poision) of war.