Though much maligned by his contemporaries, who thought him a "cold calculating owl," incapable of cultivating cordial relations, Halleck was nonetheless recognized as a man of great intellect. Nicknamed "Old Brains," he brought professionalism and organization to an army saddled with political appointments and militia mentality. He correctly placed priority on the war in the West, and made every effort to initiate and sustain simultaneous advances across a broad front. His dispatches to the field characteristically were petulant and argumentative, a trait that drew the ire of commanders who faced unforeseen difficulties. Consequently, he was the target of vitriolic outbursts in many postwar memoirs. His abilities are best appreciated when divorced from the personal animosities that clouded his every effort.
Herman Hattaway and Michael D. Smith, "Halleck, Henry Wager," American National Biography Online, February 2000, http://www.anb.org/articles/04/04-00455.html.