Sargent
spent four months in France working on the preliminary
studies for Gassed. He received a nominal fee of three-hundred
pounds for his painting, which was commissioned as a centerpiece
for a planned Hall of Remembrance at the Imperial War
Museum.
The
original conception of the proposed painting was one of
American and British troops helping one another. Sargent
came upon the idea of showing wounded soldiers after witnessing
a field of gassed and blinded men following a battle at
Le Bac-du-Sud, where German forces used mustard gas on
the 8th and 99th brigades of the 3rd and 2nd divisions.
The
Imperial War Museum has a page which briefly discusses
Sargent here.