Sulfanilamide
Before the introduction of antibacterial compounds or modern antibiotics, infection was a more likely cause of death than a wound. In World War I, medics had only saltwater and alcohol to wash wounds, and, while they understood infection, lacked the ability to treat it. That changed in World War II, with the introduction of sulfanilamide. Sulfanilamide or sulfa was an antibacterial powder, issued to American soldiers.
Sulfanilamide was part of a compound called Prontosil, an industrial dye used for wool and leather. In 1930s Germany, a number of scientists were working to find an antibacterial compound, testing available industrial chemicals. During the course of their tests, they discovered that sulfanilamide was effective against the streptococcus bacteria. By 1935, it became clear that the drug was effective; sulfanilamide was isolated from Prontosil.
The U.S. government issued sulfa powder, a white powder, to American troops to apply to wounds, as well as sulfa tablets to prevent dysentery. Sulfa powder could reduce the risk of death from serious injuries, like gunshot wounds, but could also be used to prevent infection in less severe cuts and scrapes.
Dysentery was common in the South Pacific, and without access to sulfa tablets, Japanese troops were significantly weakened by the intestinal condition. American troops, with access to sulfa tablets, were more able to effectively resist dysentery and remain more capable of fighting effectively.
Sulfanilamide played an essential role in the health of American troops in World War II, helping to support an eventual Allied victory. Sulfa has been long-since replaced by an array of more effective drugs, but this innovation saved American lives in the war, and reduced the rate of death from infection on the home front.