You would be correct that it is an anti-septic, specifically sulfa powder, which was a means to combat bacterial infection - for the science behind that... uh... I'm not that guy, but this paper might help. The drug had only become viable in the mid-30s, and it is perhaps a little ironic given that we think of American WWII films regarding it that it was a German, Gerhard Domagk, whose work made its development possible. He was given the 1939 Nobel in fact, but the Nazi government wouldn't allow him to go accept it. Of course, penicillin was miles away more effective as an anti-bacterial agent, but the major breakthrough came after war broke out, so it was really only available to the Western Allies. They still used sulfa as a first line "defense" in the field - and was credited with helping survival rates, but once penicillin was being manufactured in large amounts by the middle of the war, it was a huge medical advantage. I did a post a little while ago which compares the two, but the most obvious take away perhaps is that American wounded developed 1.5 cases of gangrene per thousand, with both sulfa and penicillin available to them. Germans, using only sulfas, developed 20 to 30 cases of gangrene per thousand. Either way an improvement on WWI, where neither existed, but I think the advantage of available penicillin over sulfa is self-evident.