From small towns to big cities and from state capitals to Washington, D.C., McClintock highlights individuals both powerful and obscure to demonstrate the ways ordinary citizens, party activists, state officials, and national leaders interacted to influence the Northern response to what was essentially a political crisis. He argues that although Northerners' reactions to Southern secession were understood and expressed through partisan newspapers and officials, the decision fell into the hands of an ever-smaller handful of people until finally it was Abraham Lincoln alone who would choose whether the future of the American republic was to be determined through peace or a sword.

Lincoln and the Decision for War illuminates the immediate origins of the Civil War, demonstrating that Northern thought evolved quite significantly as the crisis unfolded. It also provides an intimate understanding of the antebellum political system as well as Lincoln's political acuity in his early presidential career.