I saw an article in my local paper just this morning about this topic. It said that in WWII, fully 30% of the men who were wounded died. Many were killed instantly, but even those who weren't often didn't get treatment for hours, even days after they were wounded. Sulfa drugs were widely used to reduce infection, but they were basically a powder poured on the outside. They didn't do much good for wounds like those caused by cannons where the explosion blew not only shrapnel but also dirt into mens' bodies.

Today, the death rate from wounds is roughly 10%, including those who are killed instantly. One of the innovations in this war is having trauma teams operate just outside the combat zone.