An absorbing account of the destroyers-for-bases deal between Franklin Roosevelt and Winston Churchill in early September 1940. Despite Churchill's urgent pleas, culminating in his famous dispatch of July 31, 1940 -- "Mr. President, with great respect, I must tell you that in the long history of the world, this is a thing to do now" -- Roosevelt delayed acting until he had devised the stratagem of trading the destroyers for bases, which gave him political cover and provided the legal loophole ("the comma that saved a kingdom") through which his administration could jump. Shogan sees Roosevelt's maneuvers as giant steps on the road to the imperial presidency; he charges F.D.R. with twisting the law, violating neutral obligations, flouting the Constitution, hoodwinking the public, and distorting the political process. Though some of these judgments are hyperbolic, even those inclined to grant Roosevelt the benefit of the doubt can read Shogan's account with profit. The work sustains a fine narrative pace and includes a wide range of well-drawn biographical sketches.