The 39-year-old actor will also produce the film, reported Variety.
The film is based on the 1999 book of the same name by Anthony Lloyd, an English journalist and war correspondent.
Gavin O'Connor is attached to direct and produce, along with Scott LaStaiti.
"'My War Gone By' is a brutal yet sensitive story which addresses both the nature of addiction and the experience of war. I was struck by Anthony's work and words, experiences, and for me his is an important voice and an important book," Hardy said.