Hindsight, the historian's chief asset and his main liability, has enabled all historical writers to know that the decade of the 1850's terminated in a great civil war,"" writes Potter, the dean of Civil War scholars who died in 1971. Challenging hindsight, he achieves both casual coups and insights to which others would have devoted whole books--the underestimated firmness of Presidents Taylor and Buchanan, the propaganda buildup of John Brown, the neglected champions of extending the Missouri Compromise westward. Among these ""revisionist"" triumphs, the most striking is Potter's portrayal of Stephen Douglas as a principled, progressive politician whose antislavery stand of 1854 best characterized him, based as it was on a campaign to give the Transcontinental Railroad a northern route. Douglas' later bravery in openly stressing the threat to the Union is contrasted with the wily maneuvers of Sumner and Webster. Yet Potter makes no plea that the war could have been averted. On the contrary, though the book as edited and completed by Fehrenbacher, avoids a full explicit judgment on the question, it adds up to a confirmation of the view that slavery--not tariffs or any other economic, cultural or regional quarrel--was the decisive, irreconcilable issue. The series of compromises including Dred Scott, the Compromise of 1850 and the Kansas-Nebraska Act ""conspicuously failed to accomplish what was expected of them, either by their advocates or by their opponents,"" and ""strangely combined theoretical significance with trivial consequences."" The book's own richness provides a basis for specific scholarly pro and con arguments but the audacious sweep of Potter's own approach will not soon be matched.