Complex sentence: Although McCain was badly wounded, his captors refused to treat his injuries, beating and interrogating him to get information; he was given medical care only when the North Vietnamese discovered that his father was a high-ranking admiral.
Split into simpler sentences: Although McCain was badly wounded, his captors refused to treat his injuries. They beat and interrogated him to get information, and he was given medical care only when the North Vietnamese discovered that his father was a high-ranking admiral.