McPherson published "This Mighty Scourge" in 2007, a series of essays about the American Civil War. One essay describes the huge difficulty of negotiation when regime change is a war aim on either side of a conflict. "For at least the past two centuries, nations have usually found it harder to end a war than to start one. Americans learned that bitter lesson in Vietnam, and apparently having forgotten it, we're forced to learn it all over again in Iraq." One of McPherson's examples is the American Civil War, in which both the Union and the Confederacy sought regime change. It took four years to end the war.