Edited sentence: Finally he misunderstood the demands of Unionists in the border states, who warned they would not support an invasion of the Confederacy.He "underrated the gravity of the crisis"; overestimated the strength of Unionist sentiment in the South and border states; and assumed that he could call the bluff of the insurrectionists, who would eventually fade away.Historian Allan Nevins argues that Lincoln made three serious mistakes in believing that he could preserve the Union, hold government property, and still avoid war