“ Halleck’s position as a soldier is easily defined by his uniform success as an administrative official, his equally uniform want of success as an officer at the head of large armies in the field, and the popularity of his theoretical writings on war. ”

“ His influence, for good or evil, on the course of the greatest war of modern times was greater than that of any soldier on either side save Grant and Lee, and whilst his interference with the dispositions of the commanders in the field was often disastrous, his services in organizing and instructing the Union forces were always of the highest value, and in this respect he was indispensable.
Besides Military Art and Science, Halleck wrote Bitumen, its Varieties, Properties and Uses (1841) ; The Mining Laws of Spain and Mexico (1859) ; International Law (1861; new edition, 1908) ”

“ He was also director of a quicksilver mine, and in 1855 he became president of the Pacific & Atlantic railway. On the outbreak of the Civil War he returned to the army as a major-general, and in November 1861 he was charged with the supreme command in the western theatre of war. ”