Lincoln's telegraph operator, David Homer Bates, kept a diary from November of 1863 through early June of 1865. The diary, published for the first time in its entirety, records Bates's observations of the Civil War as it was fought in all areas of operation as well as detailing the centrality of the telegraph to the Union war effort. The diary is preceded by a brief, but thorough, history of the development of the military telegraph by editor, Donald Markle, a retired cryptologist in the U.S. Intelligence Service of the Defense Department. In addition Markle's introductions to each diary chapter provide historical context, highlighting telegraphic activity as well as the political and military events of the period. The book is thoroughly annotated.