Literally, "sulfur island" (3,4)
I believe the answer is:
iwo jima
'literally sulfur island' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for iwo jima that I've seen before include "Largest of the Japanese Volcano Islands, heavily fortified in World War II" , "site for WWII battle" , "Battleground" , "Jap. island (Nineteen forty five battle)" , "fierce battle" .)