Lee was an avid reader of Northern newspapers smuggled across the lines. From them he gleaned not only bits of military intelligence but also – and more important in this case – information about Northern politics and the growing disillusionment with the war among Democrats and despair among Republicans. One of Lee’s purposes in the Maryland invasion was to intensify this Northern demoralization in advance of the congressional elections in the fall of 1862. He hoped that Confederate military success would encourage antiwar candidates. If Democrats could gain control of the House, it might cripple the Lincoln administration’s ability to...