Complex sentence: In terms of photography, the American Civil War is the best covered conflict of the 19th century and presaged the development of wartime photojournalism in World War II, the Korean War, and the Vietnam War.
Split into simpler sentences: In terms of photography, the American Civil War is the best covered conflict of the 19th century. It presaged the development of the wartime photojournalism of World War II, the Korean War, and the Vietnam War.