Who were the dirty dozen?

The Dirty Dozen may have been a group of convicts that were released from prison for "suicide" type combat missions in WW II, with the promise of release if they survived the missions. The movie was based on the novel by E.M. Nathanson, the script has no specific historical antecedent, although it has been a common practice in wars to place criminals in the front lines with the promise of a full pardon if they survive. Much has been written about whether something along the lines of The Dirty Dozen actually occurred during World War II, but there is little evidence one way or another. In essence, therefore, the film should be treated as entirely fictional. It does not claim to be based on a true story, which is fortunate, because, when it comes to military details, the production often gets things wrong.